RESEARCH TEAM GRANTS IN ANTARCTIC SCIENCE 2005 FINAL REPORT
I. PROJECT PRESENTATION
PROJECT TITLE CODE Stability and recent behavior of glaciers in the Antarctic Peninsula - the interactions with ice shelves ARTG-02 PROJECT DIRECTOR SIGNATURE
Anja Wendt
CONTACT INFORMATION [email protected] - (63) 234 531 - Arturo Prat 514, Valdivia, Región De Los Ríos MAIN INSTITUTION CECS PERIOD INFORMED 2007 - 2010
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Researchers’ information
1.MAIN RESEARCHER (Complete Name) SIGNATURE Anja Wendt
WORKING ADDRESS PHONES EMAIL Av. Arturo Prat 514, Valdivia 63-234585 [email protected]
2.MAIN RESEARCHER (Complete Name) SIGNATURE Francisca Bown
WORKING ADDRESS PHONES EMAIL Av. Arturo Prat 514, Valdivia 63-234564 [email protected]
3. MAIN RESEARCHER (Complete Name) SIGNATURE Rodrigo Zamora
WORKING ADDRESS PHONES EMAIL Av. Arturo Prat 514, Valdivia 63-234529 [email protected]
1.ASSOCIATED RESEARCHER (Complete Name) SIGNATURE Jorge Carrasco Cerda
WORKING ADDRESS PHONES EMAIL Avda. Portales 3450, Estación 2-436 4519 [email protected] Central, Santiago. 2.ASSOCIATED RESEARCHER (Complete Name) SIGNATURE Juan Quintana
WORKING ADDRESS PHONES EMAIL Avda. Portales 3450, Estación 2-436 4531 [email protected] Central, Santiago. 3.ASSOCIATED RESEARCHER (Complete Name) SIGNATURE Gino Casassa
WORKING ADDRESS PHONES EMAIL Av. Arturo Prat 514, Valdivia 63-234540 [email protected]
4.ASSOCIATED RESEARCHER (Complete Name) SIGNATURE Andrés Rivera
WORKING ADDRESS PHONES EMAIL Av. Arturo Prat 514, Valdivia 63-234543 [email protected] 3 5.ASSOCIATED RESEARCHER (Complete Name) SIGNATURE José Andrés Uribe
WORKING ADDRESS PHONES EMAIL Av. Arturo Prat 514, Valdivia 63-234544 [email protected]
6.ASSOCIATED RESEARCHER (Complete Name) SIGNATURE Claudio Bravo . WORKING ADDRESS PHONES EMAIL Av. Arturo Prat 514, Valdivia 63-234538 [email protected]
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II. EXECUTIVE SUMMARY
This section should have a maximum of 5 pages long. Summarize the most relevant achievements of the ENTIRE PERIOD indicating:
1) Those explicitly related to the research activities and outcomes, 2) Activities and possible projections of international collaboration, 3) Results of the training of postgraduate students and young researchers, 4) The possible links to other national researchers either as groups and centers or, as individual researchers 5) Outputs of dissemination activities to the scientific community and outreach to non-specialized public. 6) Others either unexpected and/or that you consider significant
Please consider that the contents of this section will be published in CONICYT web site and/or reports that may be eventually printed and distributed.
The Antarctic Ring project ARTG‐02 was realized from 2007 to 2010, period in which we deployed a multiscale/multiapproach working plan characterized by a strong field component in different locations of the Antarctic Peninsula (AP).
The project focused on the Wordie Ice Shelf/Fleming Glacier system due to its key location in a highly‐dynamic area. The AP is indeed a climatic hot spot, which forms part of the world’s largest ice reservoir and has a significant atmospheric and oceanographic influence on the rest of the globe. Therefore the cryospheric changes occurring in that region are of fundamental importance. So far, ice shelf break‐off leading to inland glacier retreat has been well reported for the northern portion of the AP. The former Wordie Ice Shelf, located to the west of the AP, was really the first ice shelf reported to collapse in the AP. It suffered a large break‐up by the end of the 1980s, and although it was located well to the south (69°S) of the rest of the collapsing ice shelves in the AP, its continued disintegration along the past 21 years has led to its virtual disappearance by 2010. Union Glacier (80°S) draining into Ronne Ice Shelf, West Antarctica, was also studied as part of this project, since it represents a contrasting case study of a theoretically stable glacier flowing into a still undisturbed ice shelf in a region of inner Antarctica which has not yet experienced significant warming.
The main aim of the project was to characterize the glaciological setting of Fleming Glacier, the largest glacier in Wordie Bay, to investigate its response to the loss of its buttressing ice shelf. Surface topography data of this glacier were available from previous airborne campaigns of CECS with international collaborators, a satellite altimetry mission
5 and our own airborne survey system, allowing determination of the most recent ice elevation changes of Fleming Glacier. These measurements were estimated as highly‐ precise which is demonstrated by confident analysis of data sets biases. In the period between 2004 and 2008 a clear thinning is identified which decreases from about 4 m per year at the ice front to a value of 0.7 m per year at the highest part of the surveyed profile (1070 m a.s.l.). This altitudinal pattern is similarly found between 2002‐2008 and 2004‐2008, suggesting a decadal trend. Ten months of GPS data collected in 2009 provide an independent estimation of height changes and support these findings.
Likewise, ice flow velocities from different dates were compared to provide an insight into ice flow changes. Our GPS‐derived velocities agree with results from the 1990s and both confirm higher ice flow velocities than in the 1970s. Optical and radar satellite data acquired between 1989 and 2010 revealed an acceleration of the fast–moving glacier terminus, which attained a maximum velocity of about 2800 m/yr in 2010. In summary, in‐ situ and remote sensing tools revealed that Fleming Glacier has accelerated 30‐50% in comparison to the oldest available data in the 1970, giving indication of prevailing disequilibrium in response to the loss of the Wordie Ice Shelf. Conversely, based on our measurements we conclude that Union Glacier, remains in a steady‐state due to the conditions of Ronne Ice Shelf which seems non susceptible of disintegration in the near future. Mean velocities at Union Glacier are two orders of magnitude lower than in Fleming Glacier.
Estimation of ice volumetric discharges at the grounding line were performed based on the resulting velocity data in combination with ice thickness data from different pre‐ existing and new sources at flux gates crossing the glaciers. At present day, the ice volume flux at Fleming Glacier is estimated between 8 and 10 cubic kilometre per year, suggesting a significant increment since 1989. Accordingly, the contribution of this region to sea level rise must have also increased. Comparison of ice discharge with snow accumulation allows to estimate a mass imbalance for Fleming Glacier of 83 to 130% in 1989 and more than 160% imbalance in 2010. When converted to Sea Level Equivalent (SLE), the current contribution can be estimated to ~ 0.012‐0.017 mm/yr, which has doubled in comparison to 1989.
Long‐term climate variability along the Antarctic Peninsula shows distinctive patterns which overall, follow the tendency of atmospheric warming and increased precipitation. Among the most reliable is the large increase in minimum temperatures mainly in winter, thus reducing the diurnal thermal oscillation, as well as the lower frequency of cold nights. Annual precipitation shows strong interannual variability with increasing frequency of days with high precipitation. As for the type of precipitation, in the case of Eduardo Frei station, snowfall between 1970 and 2008 was detected to decrease
6 concomitant to the opposite trend for rain. This finding is consistent with temperature changes previously described. At a local and short‐term scale, there is a good characterization of the meteorology of the southern AP using the Fleming Automatic Weather Station (69°32’S, 66°1’W, 1057 m a.s.l) that operated between December 2007 and December 2008.
The observed precipitation in AP meteorological stations is closely linked to the frontal activity and circulation patterns associated to the so called Antarctic Oscillation. The link of Antarctic precipitation to the sea surface temperatures (SST) is also strong and involves the whole Southern Pacific Ocean. Accordingly, El Niño Southern Oscillation (ENSO), having an utmost worldwide meteorological impact, does also affect atmospheric circulation in the surroundings of the study area. In particular, ENSO produces blocking‐ high pressure cells on the western side under the El Niño phase and negative precipitation anomalies prevail. The ultimate cause of atmospheric warming can also be found on large scale phenomena such as the positive trend of the Antarctic Oscillation Index (AAO) during the last decades due to enhanced westerlies which bring the warmer maritime air over the AP.
A strong international collaboration existed throughout the project. The interaction with Dr. Konrad Steffen, leader of the NSF‐funded project ʺStability of Larsen C Ice Shelf in a warming climateʺ resulted in joint fieldwork at Larsen C and a 5 month visit of a M.Sc. Student to University of Colorado at Boulder as part of his thesis work. The remote location and methods deployed at Fleming Glacier implied complex logistics supported by a number of institutions; British Antarctic Survey (BAS), Instituto Antártico Chileno (INACh) and Chilean Air Force (FACh). At Union Glacier there is a well established cooperation with the private company Antarctic Logistics and Expeditions (ALE) which has resulted in fruitful work during the last three seasons. In addition, the project benefited from other previous alliances of CECS which allowed the availability of prominent airborne and geophysical data in the AP. Several consulting from foreign experts, short visits, seminars, presentations at international congresses and staff meetings were also a key input into the different stages of the project, improving the scientific approaches and fulfillment of research objectives. Overall, this resulted in three high‐ quality publications as the outcome of the project.
In 2010, two International Conferences were organized by CECS with the partial financial support of the Ring project. The Glaciological Conference ʺIce and Climate Change: A View from the Southʺ (VICC 2010) was held in February when a special Antarctic session was the opportunity to bring the most recent research to discussion. In October, CECS and Universidad Austral co‐organized the II International PAGES Symposium ʺReconstructing
7 Climate Variations in South America and the Antarctic Peninsula over the last 2000 yearsʺ. The conference brought leading experts from a broad range of earth sciences disciplines.
The project staff was also constantly open to dissemination activities and the public awareness through consulting, specific seminars to a variety of public, oral and written channels. The participation of one of our project members as scientific expert in the delegation of President of the Republic Sebastián Piñera and President of Ecuador Rafael Correa on a trip to the Antarctic Peninsula gave the opportunity to provide glaciological information at the highest public level. A continuous participation in dissemination activities were especially devoted to the high school community such as “Curso de Glaciología, Patagonia y Antárticaʺ, “Científicos por un mes” and “1000 científicos 1000 Aulas”, in addition to numerous oral presentations at several institutions, general public publications and graphic exhibitions.
Capacity building was a relevant issue within the framework of this research. By the end of the project, there is one undergraduate student that effectively has obtained the degree (in the area of Meteorology) while there are other two undergraduate level students with still ongoing research (Geography and Informatics Engineering). At the postgraduate level, one student is about to obtain his Masters degree (in Geographical Information Systems and Remote Sensing) during the first semester of 2011 whereas two extra students were recruited at the final stage of the project (Master in Antarctic Sciences). All of them have made important contributions to the project and are expected to graduate within the short‐term.
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III. RESULTS IN RESEARCH
Use a maximum of 20 pages in this section in order to inform the results of the research activities during the entire period of the project. The information of this section is strictly confidential and the reviewers are completed by a non‐disclosure agreement. In order to fill up this section please follow the instructions: a) Organize this section according to the specific objectives of the Project, mentioning all changes, modifications or replacements. b) If the research team considers necessary to mention negative results and requires space to discuss them it should use this section for that purpose. c) Include all appendices that you consider necessary. Limit the figure number to those that explain better what you try to convey in the text. d) If there are papers in progress related to the research results it is a good idea to include them in this section and make reference to them in the text rather than repeating the entire information in the report. These are asked as supplementary files to this report.
9 The Project entitled “Stability and recent behavior of glaciers in the Antarctic Peninsula ‐ the interactions with ice shelves” was initiated in 2006 in a joint research effort of Centro de Estudios Científicos (CECS) in association with Dirección Meteorológica de Chile (DMC). The proposal was part of the 2007/2008 International Polar Year (IPY) and its main aim was to research the glacier responses to climate change in the Antarctic Peninsula (AP), for gaining a better understanding of current ice dynamics in a region with prominent environmental changes and enhanced contribution to sea level rise. The project was focused on the Wordie Ice Shelf/Fleming Glacier system due to its key location in a highly‐dynamic area. The AP is indeed a climatic hot spot, which forms part of the world’s largest ice reservoir and has a significant atmospheric and oceanographic influence on the rest of the globe. Therefore the cryospheric changes occurring in that region are of fundamental importance. So far, ice shelf break‐off leading to inland glacier retreat has been well reported for the northern portion of the AP. The former Wordie Ice Shelf, located to the west of the AP, was really the first ice shelf reported to collapse in the AP. It suffered a large break‐up by the end of the 1980s, and although it was located well to the south (69°S) of the rest of the collapsing ice shelves in the AP, its continued dis‐ integration along the past 21 years has led to its virtual disappearance by 2010 (Fig. 1).
Fig. 1 Ice frontal positions of Wordie Ice Shelf between 1966 and 2010 (updated from Wendt et al., 2010).
10 The current dynamics and instability of Fleming Glacier, which calves into the former Wordie Ice Shelf, strongly suggested us the existence of a feedback mechanism related to the loss of the buttressing force as the ice shelf disintegrated. This statement was supported by analysis of other AP ice shelves, which, unlike Fleming Glacier, still experience a buttressing force from the respective ice shelves and thus have exhibited a more stable condition in recent years. The large‐scale effects of the glacier‐ice shelf interactions in the southern AP are rather complex and the field contingencies along the project lifetime have imposed non‐negligible limitations on computing exact ice volume output to the ocean. However, we have made significant progress in estimating the present rates to global sea‐level rise contributed by this region. In summary, after three years of research, novel methods and scales have been applied within the frame of this project, contributing with enhanced glaciological knowledge of this portion of the Antarctic Peninsula. A more detailed description is provided below according to specific objectives defined at the beginning of the project in 2006.
Objective 1: Determine ice elevation changes
Ice elevation changes at Fleming Glacier have been determined using preexisting surface topography data and new measurements conducted either by the project team itself or in collaboration with international partners (see section IV). Table 1 lists the details of the individual campaigns and Figure 2, the surveyed tracks.
Tab. 1 Airborne campaign data available for Fleming Glacier
Airborne Campaign Date Airplane Instruments Organizer
HIELO I 11‐2002 P3 ATM NASA/CECS/Chilean Navy
HIELO II 11‐2004 P3 ATM NASA/CECS/Chilean Navy
HIELO III 10‐2008 P3 ATM NASA/CECS/Chilean Navy
Anillo 12‐2008 Twin Otter CAMS CECS
As part of the second expedition to Fleming Glacier in 2008, a laser scanning survey was conducted onboard a Chilean Air Force Twin Otter aircraft using the CECS Airborne Mapping System (CAMS). The flight track was designed to repeat older flight lines, an ICESat track and to scan the actual ice front of Fleming Glacier (see Fig. 2). CAMS consists of a Riegl laser mirror scanner (LMS‐Q240‐60) combined with kinematic GPS, an inertial measurement unit and a digital camera to retrieve orthophotos. The laser scanner works with an effective measurement rate of 10,000 shots per second, resulting in a uniform pattern with a point measurement each ~1.5 m distance on the ground, when flying at an altitude of 400 m above the surface. The vertical accuracy of these measurements is 11 estimated to be 0.2 m. In total, surface topography data could be recorded along a track more than 500 km long and approximately 400 m wide.
Fig. 2 Airborne and spaceborne laser scanning data available for Fleming Glacier. Black dots and triangles indicate the location of temporal GPS occupations and the semi‐continuous GPS station, respectively.
The quality of these measurements could be confirmed by a comparison of the data with the results from the 2008 NASA/CECS campaign that was conducted about 2 months before the 2008 CAMS campaign. Because there are no overlapping measurements over bedrock to compare the two datasets, the DEMs of the undisturbed ice surface were compared. Crevassed zones were excluded from comparison because the high ice flow velocities (see Objective 2) caused a displacement of up to 200 m within the 2‐month period. The mean offset between the datasets amounts to 0.03 m with a standard deviation of 0.15 m with no significant trend.
By comparing the high‐resolution CAMS data set with the measurements from 2002 and 2004, respectively, elevation change rates can be derived. Fig. 3 shows the 2008‐2004 elevation differences plotted against surface height (Wendt et al., 2010). Data have been median‐filtered in elevation bands of 1 m to smooth out the influence of crevasses. There is a negative elevation change rate of ‐0.7 m/yr all the way from the ice front (maximum change rate of ‐4.2 m/yr) to the highest part of the profile at 1070 m a.s.l. The 2008‐2002 difference shows a similar distribution with the highest change rate of ‐3.7 m/yr near the
12 ice front. The difference between the two change rates, that would indicate an acceleration of ice thickness loss, is not significant at the 95% confidence level.
Fig. 3 Elevation change rates at Fleming Glacier 2002 → 2008 (red) and 2004 → 2008 (blue) plotted against absolute elevation in 2008. 95% confidence intervals are drawn in light red and light blue, respectively. ICESat elevation rates are shown in black, the GPS rate in green.
Another independent data source for elevation changes are laser altimetry measurements from ICESat (Ice, Cloud, and land Elevation Satellite) that operated from 2003 to 2009 (Shuman et al., 2006). Elevation change trends are derived by an adjustment procedure of typically 4 observations that solves for mean height, height change rate, and slope (Zwally et al., 2011). For Fleming Glacier there are basically two relevant ICEsat tracks, mapped in white in Fig. 2. They cross the glacier at an elevation of about 600 m. For the adjacent Airy Glacier the lowest data points are at an elevation of about 200 m, there are no data in immediate proximity to the ice front. The ICESat elevation change rates confirm the airborne‐derived trends within the confidence intervals and also show altitudinal dependence. The high scatter of the ICESat rates at Fleming Glacier is due to the fact that the ICESat tracks cross the whole width of the glacier while the airborne rate just represent a central profile on the glacier.
The data from the semi‐continuous GPS station that operated from December 2008 to October 2009 at Fleming Glacier also serve as a single observation of surface height change. The GPS processing described in more detail in Objective 2 gives an elevation change of the top of the antenna pole of 7.0 m ± 0.01 m. This value has to be corrected for snow accumulation of 2.6 m ± 0.03 m derived from the height of the antenna pole above the snow surface at the beginning and at the end of the measurement period and for slope of the glacier surface because the marker moved by more than 200 m. This correction was derived from the airborne laser scanning data and amounts to 3.2 m ± 0.26 m. The final elevation rate change is thus ‐1.4 m yr‐1 ± 0.3 m yr‐1 (marked in green in Fig. 3). For the 13 interpretation of this value one has to keep in mind that the change rate is derived from just 10 months of observation, but it fits nicely within the range covered by the other observations.
Objective 2: Determine recent ice flow fluctuations of glaciers currently draining into ice shelves and of those glaciers having lost their buttressing ice‐shelf
Case study 1: Fleming Glacier
Ice flow velocities at Fleming Glacier were first measured in the 1970s some 40 km from the grounding line (Doake 1975). Apart from previous comparisons with radar satellite velocities from the mid 1990s by Rignot et al. (2005), our field campaign in 2008 provided the first opportunity to undertake precise, in situ re‐measurement of these data.
Two of the sites surveyed by Doake using optical resection were observed by dual‐ frequency GPS for 12 days. The data were processed kinematically with a reference station on a nunatak located close to the base camp used in 2007 and 2008. Velocities were determined by a least square adjustment that gives an RMS value of a single observation of 0.02 m. The displacements derived from a time span of 12 days can be extrapolated to annual velocities resulting in an uncertainty of few cm per year, assuming that there are no seasonal changes in ice flow. This assumption is widely accepted and was also used by Doake and Rignot et al. to derive their annual velocities. Since both the measurements in of Doake in 1974 and our measurements in 2008 were carried out in December, and the radar data used by Rignot et al. (2005) were acquired also in the summer, seasonal changes should not affect the comparison.
Velocity and respective errors of the comparison of the three dates are listed in Table 1 of Wendt et al. (2010). Our GPS measurements confirm the higher flow velocities that have been measured in the 1990s, and moreover, these rates have remained nearly constant without any significant acceleration within the large error margins of the interferometric velocities. The directions of the 1974 and 2008 measurements are very similar (Table 1), however the different angles obtained by Rignot et al. (2005) are probably related to the higher uncertainties of the interferometric method, when determining ice flow direction under unfavorable geometry of the intersecting angle of the satellite tracks.
In order to study recent velocity fluctuation in more detail, a permanent GPS station was installed between locations A and C in December 2008. Due to the lessons learned from former installations, the dual‐frequency GPS receiver operated successfully through October 2009 when it was de‐installed by the last expedition of the project. The installation of the antenna and the solar panel on more than 5 m high frames reliably prevented snow burial, while the power supply by high‐capacity lead gel batteries and solar panels was ample enough to assure data reception during most of the polar night with just 2 weeks of missing data in August. The acquired data were processed in collaboration with colleagues from the University of Technology Dresden, Germany (see IV NATIONAL AND INTERNATIONAL COLLABORATION) using the precise point positioning approach of Bernese GPS software 5.0. The mean velocity calculated from daily solutions
14 amounts to 255.8 m/yr and fits very well with the field measurements of temporal GPS occupations in 2008.
Fig. 4 Ice flow velocities derived from a running 10‐day window of GPS data (black dots) and the linear trend (red line) showing the velocity increase.
Nevertheless, looking at the daily residuals and calculating velocities for running windows of shorter time spans, gives insight into velocity changes on shorter time scales (Fig. 4). For the interpretation of this result, one has to keep in mind that it originates from highly precise data covering less than one year of observations. A potentially expected seasonal signal with higher velocities in summer and lower ones in winter can be discarded from Figure 4, instead there is a clear yearly increase in velocity of 6.1 m/yr. A trend of this magnitude would be difficult to detect in the interferometric processing of data of old generation radar satellites like ERS‐1/2 or Radarsat‐1 that were used by Rignot et al. (2005). Alternative and more precise Synthetic Aperture Radar data come from TerraSAR‐X providing X‐ band data with up to 1 m resolution that have been successfully used to derive ice flow velocities for the glaciers draining into former Larsen B ice shelf (Rott et al., 2010). Currently, data covering Fleming Glacier from the ice front all the way up to the GPS sites are being acquired in collaboration with the German Aerospace Center DLR to generate an archive for the analysis of ice flow velocities by speckle tracking (Fig. 5).
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Fig. 5 Amplitude image of TerraSAR‐X acquired over Fleming Glacier on 29 of November 2010. Flight direction is to the right, look direction is up.
For the lower reaches of fast flowing glaciers, the interferometric signal of C‐band radar (ERS, Radarsat and Envisat) typically decorrelates thus inhibiting the determination of ice flow velocities. Therefore, image correlation techniques have been applied using both pairs of optical and SAR data to determine ice flow velocities near the glacier terminus for different years. Table 2 lists images from Landsat and Envisat satellites used in the study. There were no suitable ASTER pairs with time differences not larger than 3 months available in the respective data bases.
Tab. 2 Acquisition dates and resolution of optical (Landsat 4 and Landsat 7) and SAR (Envisat) satellite images used for velocity determination.
Sensor Observation dates Resolution Landsat 4 1988‐12‐25, 1989‐02‐20 30 m Envisat 2006‐01‐29, 2006‐03‐05, 2006‐05‐14 20 m Envisat 2009‐07‐12, 2009‐08‐16, 2009‐09‐20, 2009‐10‐25 20 m Landsat 7 2009‐11‐10, 2010‐02‐14 15 m Envisat 2010‐01‐03, 03‐14 20 m
Optical and SAR data were treated independently. Landsat data were processed by image matching using orientation correlation operated in the frequency domain (Haug et al., 2010). Instead of the intensities themselves, intensity gradients are matched to enhance contrast and to produce more reliable matching results. A critical preprocessing step in deriving correct displacements from the images is the precise image coregistration to account for differences in the acquisition geometry. This is particularly difficult in the images used, because most of the scenes map either moving glacier surface or ocean. Ground control points (GCPs) on stable bedrock were selected manually to derive the linear offsets between the 2 images. Standard deviations for the offsets from individual GCPs are in the order of 0.3 pixels. The size of the matching windows has to be selected carefully to be large enough to contain representative surface features to match and to 16 comprise the maximum displacement between the images. On the other hand, the windows have to be small enough to be characterized by only one type of movement. Finally, a window size of 1500m x 1500 m was used. The correlation function is derived for each of the windows by multiplying the fast Fourier Transform (FFT) of one image window with the conjugate FFT of the other one. Subpixel accuracy is obtained by adjusting a parabolic function to the correlation matrix of each window. The result for the 2009/2010 Landsat image pair is shown in Fig. 6.
SAR data from Envisat were processed using the offset tracking tools within the GAMMA SAR and Interferometry Software (Strozzi et al., 2002). The algorithm uses normalized cross correlation of image patches of the SAR intensity images. A window size comparable to the optical images was used. The offsets are determined by fitting a two‐dimensional regression function to the oversampled values of the image patches.
Fig. 6 Ice flow velocities derived by image correlation from Landsat data from 10th November 2009 and 14th February 2010. The white line indicates the AB profile along the glacier front, the red line shows the flux gate CD for ice discharge calculation.
For a quantitative comparison of the ice flow velocities derived for different years, velocities along the glacier terminus are extracted (Fig. 7). The profile ends on bedrock outcrops on both sides and velocities were constrained to zero to account for residuals in the coregistration process. The accuracy of the derived velocity estimates can be evaluated when more than two images are available within one season, so that velocity differences can be fully attributed to uncertainties in the processing. For the year 2006 an image pair covering 35 days (29‐01 to 05‐03) as well as one covering 70 days (05‐03 to 14‐05) can be analyzed. The derived velocity fields are not independent because they both use a 17 common image, but they give some insight into the repeatability of the results. The velocities derived for March/May are on average 15.1 m/yr higher with a standard deviation of 43 m/yr. A comparison of the Landsat derived results for November 2009‐ January 2010 (96 days) and January 2010‐March 2010 (35 days) yields a mean difference of 6.4 m/yr with a standard deviation of 51 m/yr for 2 completely independent data sets. The accuracy of the 1988‐1989 Landsat pair is presumably lower because of firstly the lower resolution and secondly, because images from 2 adjacent paths and rows have been correlated. In a conservative estimation the error was determined to be in the order of 150 m/yr.
For the fast‐moving part of the profile (approximately from km 6 to 12) mean velocities are 1830 m/yr, 2267 m/yr, 2537 m/yr and 2510 m/yr for 1989, 2006, 2009 and 2010, respectively. Maximum velocities occur within about 1 km of each other and amount to 2091 m/yr, 2592 m/yr, 2793 m/yr and 2804 m/yr, respectively.
Fig. 7 Ice flow velocities of different years along the ice front of Fleming Glacier (AB in Fig. 6).
The main glacier tongue shows a clear velocity increase between 1989 and 2010 of 694 m/yr on average. Based on the above mentioned accuracies for the individual epochs, this difference can be determined with a mean error of 158 m/yr and is significant at the 99% confidence level. The resulting acceleration amounts to 33 m/yr per year. Comparison of the 2006 and 2010 measurements reveals an average velocity increase of 201 m/yr at the glacier tongue that is significant at the 95% level.
In summary, data from different in‐situ and remote sensing techniques reveal an acceleration of the glacier in the upper reaches as well as at its front in comparison to the oldest available data in the 1970 and 1980, which is present also in the most recent data.
Case study 2: Union Glacier
In contrast, a 2nd case study at Union Glacier, located at 80°S in the interior of Antarctica, south of the AP, reveals conditions near equilibrium. An intense subglacial and surface mapping in December 2008 by means of radar survey and GPS stake measurements (Rivera et al., 2010) showed the dynamical and hydrological characteristics of this glacier 18 flowing into the Constellation Inlet of the Ronne Ice Shelf, which is not supposed to be vulnerable to the disintegration process that affects ice shelves in the Antarctic Peninsula (Vaughan and Spouge, 2002) in response to widespread atmospheric warming. Rutford Ice Stream (RIS), which is a rather large contributor to the Ronne Ice Shelf, is characterized by tidally modulated ice flow (Gudmundsson, 2006), being considered stable over recent decades (Gudmundsson and Jenkins, 2009). Union Glacier, a minor ice contributor to the Ronne Ice Shelf, is characterised by a deep subglacial topography (~900 m below sea level) and ice velocities smaller than those of RIS. A comparison of the GPS‐derived stake positions in 2008 with the reconnaissance results from 2007 revealed a mean velocity of 22.6 m/yr with a maximum of 24.5_± 1 m/yr. These velocities are all one order of magnitude lower than the RIS velocities, which are typical for ice frozen to the bed (Vaughan et al., 2008) and even two orders of magnitude smaller than the velocities measured at Fleming Glacier.
The tidal analysis of a GPS station we installed on Union Glacier (79°42´S, 82°27´W) that operated for 45 days in summer 2009/2010 did not show any significant tidal signals indicating that the tidal wave did not propagated that far inland from the grounding line of the ice shelf (Gudmundsson, personal communication). Also in 2009/2010 the stake network at Union Glacier was resurveyed by GPS and enlarged. The longer observation periods in comparison to the very first measurements facilitated a more accurate velocity determination that basically confirmed the above mentioned numbers and provide a basis for high‐precision velocity change detection. GPS data that were collected during a recent campaign in December 2010 will be analysed in this respect.
Objective 3: Estimate annual ice volumetric discharges at the grounding line (of several glaciers)
To estimate annual ice fluxes, apart from ice flow velocities (see Objective 2) ice thicknesses have to be known, which is a limiting factor in many regions of Antarctica. Few flight lines from the BAS airborne radio echo sounding campaigns from the 1970s and from 1997/98 crossed the lower reaches of Fleming Glacier and are included in the compilation of BEDMAP (Lythe et al., 2001). More recent data come from the HIELO I to HIELO III missions mentioned in Objective 1 and from the ICEBRIDGE missions in 2009 and 2010. All these airborne campaigns were conducted with support of CECS. Nevertheless, only few ice thickness measurements are available from these campaigns near the ice front, because the highly crevassed surface prevents the reception of bedrock echoes.
Therefore, ice flux was calculated on a profile crossing Fleming Glacier at a surface elevation of about 250 m. Ice thickness data from the BEDMAP data base compiled from measurements before 2000 were corrected using the HIELO I ice thickness data from 2002. The elevation change rate (Objective 1) for the location of the profile is ‐2.5 m/yr. This value was used to transfer the elevation data to the epoch of the velocity data, March 2010. The ice surface velocities derived from image correlation have to be converted to depth‐ averaged velocities. The usual approach neglecting bottom sliding is using Glen´s flow law with a nonlinearity of 3 (Paterson 1994, p. 252) leading to a depth‐averaged velocity 19 that amounts to 80 % of the surface velocity. Doake (1975) determined sliding velocities in the upper reaches of Fleming Glacier of up to 30% of the surface velocity. Assuming 100% of sliding near the glacier terminus (mean velocity equals surface velocity) gives the upper bound of ice flow velocities used for the flux determination. The integrated flux across the whole profile divided into discrete sections can then be calculated summing up all individual products of ice flow velocity perpendicular to the profile, ice thickness and width of the section (e. g. Wendt et al., 2009). Depending on the amount of sliding, the ice flux leaving this flux gate amounts to between 7.9 km3/yr and 9.9 km3/yr. The formal error of this value assuming an accuracy of 100 m for ice thicknesses and 80 m/yr for ice velocities is 0.13 km3/yr.
The same calculation for the year 1989 with the velocities derived from Landsat 4 and ice thicknesses converted to the same year using a constant thinning rate gives an ice flux between 5.5 and 6.9 km3/yr with an error of 0.14 km3/yr.
Union Glacier
At Union Glacier velocity measurements from GPS and ice thicknesses from a radar depth sounder survey are available on a glacier cross section. Ice flux determination based on this data follow the same line outlined above and is described in more detail in Rivera et al. (2010) and yields a total flux of 0.10 ± 0.03km3/yr water equivalent.
Objective 4: Determine the glacier contribution to global sea level rise
The net contribution of a glacier to sea level rise can be calculated as the difference between its ice discharge and the accumulation on the area it drains. The area upstream of the profile used in the ice flux determination in Objective 3 was estimated to be 5049 km2± 500 km2. Using the same long‐term snow accumulation of 0.59 m/yr of ice as was used in Rignot et al. (2005) the total snow accumulation adds up to 3.0 km3/yr ± 0.59 km3/yr of ice. This means that following our estimates, Fleming Glacier was out of balance by 83 to 130% in 1989 depending on the assumption about basal sliding. The numbers for 2010 are between 160 and 230% and therefore considerable higher. To estimate the contribution of the glacier to sea level the above numbers have to be converted to water equivalent. We use a mean density of 900 kg/m3 instead of the density 917 kg/m3 for pure glacier ice to account for the air content in the upper firn layer. In 1989, Fleming Glacier ice flux exceeded the snow accumulation in its drainage basin by 2.25 to 3.5 km3 of water equivalent. Distributing this water volume evenly onto the ocean surface of 362 * 106 km2 gives a sea‐level equivalent (SLE) of 0.0062 mm to 0.0097 mm per year. The same numbers for 2010 are 4.4 and 6.2 km3 of water equivalent and 0.012 mm 0.017 mm SLE. Thus, Fleming Glacier almost doubled its contribution to sea level rise between 1989 and 2010.
Objective 5: Determine changes in the type of precipitation in the Antarctic Peninsula
Extreme temperature tendency at the northern tip of the Antarctic Peninsula
Through the evaluation of climate change indicators at three stations (Eduardo Frei, Bernardo O´Higgins and Arturo Prat, see Plate 1) at the northern tip of the Antarctic
20 Peninsula, we were able to identify the main tendencies and behaviour of the extreme temperature during the 1970‐2010 period. Thus, the warming revealed by this study concurs with previous results like those found in Jacobs and Comiso (1997), Comiso (2000), Turner (2005), Monaghan and Bromwich (2008) and many others. The extreme tendencies are mainly concentrated between May and August, which are the coldest months with larger variations (Fig. 8), and that this shift in the distribution explains the larger temperature trend in winter than in other seasons. The same trends are observed for the maximum temperature but much less in magnitude, explaining the decreasing thermal diurnal amplitude (Fig. 9).
Fig. 8 Minimum (a) and Maximum (b) air temperature tendencies for Eduardo Frei, Bernardo O’Higgins and Arturo Prat stations, during the 1970‐2008 period.
Fig. 9 Annual average of the diurnal thermal range (DTR) and linear tendency between 1970 and 2008 for Eduardo Frei and Bernardo O`Higgins stations.
A significant negative trend of the thermal amplitude was found with an average rate of ‐ 0.29° C/decade in Frei, and ‐051° C/decade in OʹHiggins. It can also be shown with a confidence level of 95%, that the distribution of the minimum air temperature corresponding to the percentile 10 (TN10p) at the Frei station, moves to the right (higher values of the distribution), indicating a decrease in cold nights whose trend is 6.7days/decade. Also, there is an increase in the minimum air temperatures for the percentile 90 (TN90p), which refers to the increase in warm nights, with a positive trend of 1.5 days/decade. Therefore, the average value of the minimum air temperature is 21 positively biased with the positive trends of 0.31° C/decade, which is consistent with the TN 10p and TN90p indicators presenting a positive and a negative trend, respectively. In relation with the warm days (TX90p), the analysis shows a decline whose negative trend is 5.1 days/decade
Thus, the results show a warming during night hours in the northern tip of the Antarctic Peninsula, represented by the stations Eduardo Frei and Bernardo OʹHiggins. The analysis shows a right shift of the distribution of minimum air temperature indicated by the lower frequency of cold nights and increase in warm nights. The same tendency has been observed in much of South America (Vincent et al. 2005) and Australia (Alexander and Arblaster, 2008), where the observed warming is linked to the increase in the warm nights and in particularly, it has been associated to the minimum air temperature and in a lesser extent to the maximum air temperature.
Changes in precipitation
Totals of annual rainfall in the station Eduardo Frei, Bernardo OʹHiggins and Arturo Prat, show a slightly positive linear long‐term trend with a strong interdecadal variability, with increases in the period 1970‐1990 and 2000‐2008 and a decrease between 1991‐1999 (Fig. 11). Days with intense precipitation (precipitation >10 mm) and very intense precipitation (precipitation >20 mm) have increased in Frei and OʹHiggins. Maximum rainfall in one day (index RX1day) and maximum precipitation in 5 days (index RX5day) have also increased in both stations.
Fig. 10 Interannual variability of rainfall at stations in the Antarctic Peninsula. The continuous black line represents the average annual precipitation. The segmented line is the linear trend during the whole period, and the dotted line is the linear trend for 1970‐1990, 1991‐1999 and 2000‐ 2008.
Another important factor in the precipitation behavior in the Antarctic Peninsula is related to the type of precipitation in the region. The bi‐annual precipitation distribution with their two relative maxima in March and October, are determined mainly by the greatest number of days with solid precipitation (snow) that occurs most of the year (Figure 12), with the maximum from April to October. More days with liquid precipitation occurs in 22 January and February, coinciding with higher air temperatures, where the average minimum temperature is 0.2 °C and the average maximum temperature is 3.2 °C.
Fig. 11 left: Total precipitation, snow and rain, monthly averages for Eduardo Frei station, 1971‐ 2000, right: Total annual days with snow and rain at station Eduardo Frei for 1970‐2008.
The number of days with snow in the Eduardo Frei station between 1970 and 2008 shows a negative trend of 3.5 days/decade, unlike the number of days per year with liquid precipitation which have increased in 1 day/decade (Fig. 11). This is consistent with increases in air temperature found in the region, supporting the increased occurrence of days with liquid precipitation and reduction in the number of days with snow precipitation.
Other evidence of the atmospheric warming in the Antarctic Peninsula has been the increase of days with fog in Eduardo Frei station, with a positive trend of 5.04 days/decade. Decadal scale yields an average of 28.8 days in the 1970s, only 15.6 days in the 1980s, followed by an increase to 34.3 days during the 1990s and 39 days in the last decade (Fig. 12). The observed sustained increase of day with fog in the last two decades can be associated with enhanced atmospheric stability and the presence of anticyclonic circulation. Also the positive phase of the Antarctic Oscillation started with greater intensity in the 1990s, especially in the summer season (Dec‐Feb) and autumn (Mar‐May).
Fig. 12 Frequency of foggy days per year observed at 12UTC in Eduardo Frei station.
To complement the existing networks of Automatic Weather Station (AWS) and to fill a gap in the southwestern part of the Antarctic Peninsula, an AWS was installed in December 2007 at 69°32’S, 66°1’W, 1057 m a.s.l. During the second expedition to the site in 23 December 2008 the station was maintained, data downloaded and finally the station reinstalled on a higher mast. Unfortunately, when the third expedition team visited the site again in October 2009, the AWS was not found, most probably because it was destroyed by strong winds or because it was covered by snow. Data from the installed sensors (two radiometers, thermometers, humidity sensors, barometers, anemometers and two sonic range ultrasonic sensors) were analyzed in order to characterize the meteorological setting and compare it with other stations in the region (Carrasco et al., submitted). Due to the loss of the station and the therefore reduced data recovery, a high‐ resolution analysis and comparison with the three AWS installed by the US partner project on Larsen C ice shelf in 2008 was not possible.
Objective 6: Study of the decadal climate behaviour around the Antarctic Peninsula associated to natural changes in atmospheric circulation
Atmospheric circulation patterns and precipitation
Using spatial correlation analysis we identified the relationship between precipitation in Frei, OʹHiggins and Prat stations with atmospheric variables at surface and high level fields. The annual correlation fields between the sea level pressure (SLP) and precipitation in the Antarctic region show a negative pattern on the continent with values of correlation of up ‐0.5 in the coastal region (Fig. 13). The study region in the Antarctic Peninsula (northern sector between the 62°S to 63°S latitude) indicates a correlation of 0.3. Positive values are located in lower latitudes and East Antarctica. This pattern is similar to the seasonal correlations field, except in the autumn season where this pattern is weakened and dominated by the extension of positive correlations around 50°S latitude. Higher correlations between precipitation and SLP are found in the Bellingshausen Sea occurring in summer, winter and spring seasons; reaching values of 0.7 and close to 0.6 in the northern sector of the Peninsula during spring. This inverse correlation pattern (negative) of the pressure in the ocean region to the West of the Antarctic Peninsula and observed precipitation in Frei, OʹHiggins and Prat stations is closely linked to the frontal activity and passing low pressure systems.
Fig. 13. Correlation fields between precipitation at Frei, OʹHiggins and Prat stations and the sea level, annually (left) and during spring (right) for the 1970‐2008 period.
24 Consistently, the 250 hPa zonal wind field shows a positive pattern of correlation between the westerly airflows in the upper troposphere, characterized by the existence and intensification (weakening) of the polar jet stream and increase (decrease) precipitation in Frei, Prat and OʹHiggins stations. This circulation pattern characterized by intensified westerly airflows at 250 hPa is part of the structure defined as the positive phase of the Antarctic Oscillation (Monaghan and Bromwich, 2008). The annual correlation field between precipitation and the 250 hPa zonal wind shows a pattern with positive values in the coastal region of the Antarctic continent, and negative around the 40°S ‐ 50°S, and in the interior of Antarctica (Fig. 14). Higher correlations are observed during the winter months (r = 0.5), associated to the more frequent passage of synoptic scale cyclones during this time of year.
Fig. 14. Correlation between precipitation recorded at Frei, OʹHiggins and Prat stations and the 250 hPa zonal wind, at annual level (left) and winter (right) from 1970 to 2008.
The sea surface temperature (SST) and precipitation fields are directly correlated. It is found that a scenario of positive SST anomalies at equatorial latitudes in the Pacific Ocean (warm surface water), is associated with an increase in precipitation in coastal areas of Antarctica. The Antarctic Peninsula region shows this pattern throughout the year, but it is in winter when it reaches the highest values of correlation (r = 0.4). Extreme temperatures are also strongly related to the SST in the Antarctic Peninsula, increases of SST are associated with increases in extreme temperatures, with higher correlations in the winter (r > 0.7) and autumn (r = 0.6) seasons, being always positive year‐round .
High negative correlations (~ ‐0.7) are observed throughout the year between maximum temperature and the SLP in the Bellingshausen Sea region (Fig. 15). Correlation fields show a similar structure to the positive phase of the Antarctic Oscillation (AAO with negative values on the continent and positive in the 30° ‐ 50°S band). Seasonal correlations show similar pattern in autumn (MAM), winter (JJA) and spring (SON), but this pattern is weak during the summer season.
25
Fig. 15. Annual (left) and summer (right) correlation fields between air temperature and sea level pressure for 1970‐2008.
It has been shown that the positive trend of the AAO contributes to the increases and intensification of westerly airflow (Monaghan and Bromwich, 2008 and Marshall 2002, 2003, 2006). These increases are associated with the intensification of the circumpolar trough. Analyzed correlation fields show spatial structures similar to the positive phase of the AAO, i.e., negative pressure anomalies in and around the Antarctic continent and three positive regions located in the Pacific, Atlantic and Indian oceans around the 40° ‐ 50°S band, indicating that there is a strong relationship between climate variables such as precipitation and temperature extremes and the atmospheric circulation in high latitudes.
According with Monaghan et al., (2006a and 2006 b), who studied the changes in Antarctic snowfall since 1955, including the western side of the Peninsula region; there has been an increase between 1975 and 1994 and a decrease in the 1995‐2004 period.
The overall annual daily precipitation occurrence in the northern tip of the Peninsula as recorded by Frei station, reveals similar behavior as Monaghan et al. (2006), but suggests an increase in recent years (Fig. 10). Although not statistically significant, the linear trend of the daily liquid precipitation shows a slight positive trend, while the solid shows a negative trend, suggesting a change in the type of precipitation, at least in the northern region of the Peninsula and perhaps along the its western coast. This behavior can be related with the fact that the Antarctic Peninsula is one of the most affected regions by the worldwide increase of the tropospheric temperature, being higher than the global average warming of air.
Study of the decadal climate behaviour around the Antarctic Peninsula that can be associated with natural changes in the atmospheric circulation like ENSO, PDO and AAO and glacier responses
El Niño Southern Oscillation (ENSO) is one of the major interannual variabilities that take place in the Pacific Ocean with worldwide impact in the weather patterns. Atmospheric circulation anomalies associated with ENSO also occur around the Antarctic continent, in
26 particular, a high pressure anomaly takes place just to the west of the Antarctic Peninsula under El Niño phase. In these circumstances negative anomalies in precipitation prevail in the west side of the Peninsula. This is more evident with strong El Niño as those occurred in 1982, 1987 and 1997 (Fig. 16).
Fig. 16. NCEP/NCAR Reanalysis composite of the precipitation anomalies for major El Niño events.
The precipitation data recorded at Eduardo Frei station, located in the northern tip of the Peninsula, also capture the precipitation deficit for strong El Niño events such as in 1982, 1987 and 1997 (Fig. 17). In fact, there is a good correlation between precipitation and the Southern Oscillation Index behavior, except for 1993 when El Niño was a rather weak and prolonged event. On the other hand, no correlation is found between strong La Niña phase and precipitation in Frei station.
3 30 Anomalías dePrecipitación 2 20
1 10 (mm) 0 0 Presión -1 -10
El Niño 91/95 -2 -20 El Niño 87/88 El Niño 97/98 -3 El Niño 82/83 -30 85 95 1980 1990 2000 Años IOS Frei -Prat -Ohiggins
Fig. 17. Southern Oscillation Index (SOI) and precipitation anomalies in the northern tip of the Antarctic Peninsula as measured by the Chilean stations Frei, Prat and O´Higgins.
The Antarctic Annular Mode is a low‐frequency mode of atmospheric variability that takes place in the southern hemisphere, and it is a pressure oscillation between the midlatitudes and the interior of Antarctica. A positive (negative) phase is when negative anomalies prevails pressure around the mid‐latitudinal belt (40‐65°S) while negative (positive) anomalies occur in the interior of the Antarctic continent. The positive trend of the AAO during the last decades leads to an increase in the westerlies around the Antarctica, in particular across the Peninsula, where the stronger westerly brings warmer maritime air over it. This is the cause of the warming in the Antarctic Peninsula. On the other hand, the southward shift of the storm tracks associated with high AAO index implies an increase in precipitation in the Peninsula. Figure 18 shows the high correlation between precipitation and the AAO as revealed by the NCEP/NCAR Reanalysis.
27 a
1.5 1.5 r = 0.73 1.0 1.0 0.5 0.5 0.0 0.0 -0.5 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 -0.5 -1.0 -1.0 -1.5 r = 0.73 -1.5 -2.0
1970 1975 1980 1985 1990 1995 2000 2005 -2.0
SEP-AAO Edo.Frei menos Pto Montt bc
Fig. 18. Correlation between Antarctic Annular Mode and precipitation in the Antarctic Peninsula.
References Alexander, L., and J.M. Arblaster, 2009: Assessing trends in observed and modelled climate extremes over Australia in relation to future projections. Int. J. Climatol. 29: 417–435. Carrasco, J., J. Quintana, A. Rivera, A. Wendt, F. Bown. (submitted). Meteorological behaviour derived from in situ AWS data recorded at Fleming Glacier, Antarctic Peninsula. Antarctic Science (ISI). Comiso J., 2000: Variability and Trends in Antarctic Surface Temperatures from In Situ and Satellite Infrared Measurements. J. Climate, 13, 1674–1696. Doake, C. 1975. Bottom sliding of a glacier measured from the surface. Nature 257(5529), 780‐782. Gudmundsson, G.H. 2006. Fortnightly variations in the flow velocity of Rutford Ice Stream, West Antarctica. Nature 444(7122), 1063–1064. Gudmundsson, G.H. and A. Jenkins. 2009. Ice‐flow velocities on Rutford Ice Stream, West Antarctica, are stable over decadal time‐scales. J. Glaciol. 55(190), 339–344. Haug, T., A. Kääb, and P. Skvarca, 2010, Monitoring ice shelf velocities from repeat MODIS and Landsat data – a method study on the Larsen C ice shelf, Antarctic Peninsula, and 10 other ice shelves around Antarctica, The Cryosphere 4, 161‐178, doi:10.5194/tc‐4‐161‐2010. Intergovermental Panel on Climate Change (IPCC) (2007), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon, 996 pp., Cambridge Univ. Press, Cambridge, U. K. 28 Jacobs S. y J. Comiso, 1997: Climate Variability in the Amundsen and Bellingshausen Seas, J. Climate, 10, 697–709. Lythe, M.B., D.G. Vaughan and BEDMAP consortium. 2001. BEDMAP: a new ice thickness and subglacial topographic model of Antarctica. Journal of Geophysical. Research 106(B6), 11,335– 11,351. Marshall G., 2002: Analysis of recent circulation and thermal advection change in the northern Antarctic Peninsula. J. Climate, 22, 1557‐1567. Marshall G., 2003: Trends in the Southem Annular Mode from observations and Reanalyses. J. Climate, 16, 4134‐4143. Marshall G. et al., 2006: The Impact of a Changing Southern Hemisphere Annular Mode on Antarctic Peninsula Summer Temperatures, J. Climate, 19,5388‐5404. Monaghan A. et al., 2006a: Insignificant Change in Antarctic Snowfall Since the International Geophysical Year, Science 11, 313, 827 – 831. Monaghan A. et al., 2006b: Recent trends in Antarctic snow accumulation from Polar MM5 simulations. Phil. Trans. R. Soc. A (2006), 364, 1683–1708. Monaghan A. y D. Bromwich, 2008: Advances in Describing Recent Antarctic Climate Variability, Bull. Amer. Meteor. Soc., 89, 1295–1306. Rivera, A., R. Zamora, C. Rada, J. Walton & S. Proctor. 2010. Glaciological investigations on Union Glacier, Ellsworth Mountains, West Antarctica. Annals of Glaciology 51(55), 91‐96. Rott, H., F. Müller, T. Nagler, D. Floricioiu, 2010, The imbalance of glaciers after disintegration of Larsen B ice shelf, Antarctic Peninsula, The Cryosphere Discussions 4(3), 1607‐1633, doi:10.5194/tcd‐4‐1607‐2010. Shuman, C. A., H. J. Zwally, B. E. Schutz, A. C. Brenner, J. P. DiMarzio, V. P. Suchdeo, H. A. Fricker 2006. ICESat Antarctic elevation data: Preliminary precision and accuracy assessment, Geophysical Research Letters 33(L07501), doi:10.1029/2005GL025227. Strozzi, T., Luckman, A., Murray, T., Wegmüller, U. and Werner, C., Glacier motion estimation using SAR offset‐tracking procedures, IEEE Transactions on Geoscience and Remote Sensing 40, 11, 2384‐2391, 2002. Turner J. et al., 2005: A positive trend in western Antarctic Peninsula precipitation over the last 50 years reflecting regional and Antarctic‐wide atmospheric circulation changes. Annals of Glaciology, 41, 85‐91. Vaughan, D. G. and J. R. Spouge, 2002, Risk Estimation of Collapse of the West Antarctic Ice Sheet, Climatic Change 52(1‐2), 65‐91, doi: 10.1023/A:1013038920600. Vaughan, D.G., H. Corr, A. Smith, H.D. Pritchard and A. Shepherd. 2008. Flow‐switching and water piracy between Rutford Ice Stream and Carlson Inlet, West Antarctica. J. Glaciol, 54(184), 41–48. Vincent L. et al., 2005: Observed Trends in Indices of Daily Temperature Extremes in South America 1960‐2000. J. Climate, 18, 5011‐5023. Wendt, A., G. Casassa, A. Rivera, and J. Wendt (2009), Reassessment of ice mass balance at Horse‐ shoe Valley, Antarctica, Antarctic Science 21(5), 505‐513, doi:10.1017/S0954102009002053. Wendt, J., A. Rivera, F. Bown, A. Wendt, R. Zamora, G. Casassa & C. Bravo (2010), Recent ice elevation changes of Fleming glacier in response to the removal of Wordie ice shelf, Antarctic Peninsula, Annals of Glaciology 51(55), 97‐102. Zwally, H. J., Li, J., Brenner, A. C., Beckley, M., Cornejo, H. G., DiMarzio, J., Giovinetto, M. B., Neumann, T. A., Robbins, J., Saba, J. L., Yi, D., Wang, W. 2011, Greenland ice sheet mass balance: distribution of increased mass loss with climate warming; 2003–07 versus 1992–2002, Journal of Glaciology 57(201), 88‐102. 29 IV. NATIONAL AND INTERNATIONAL COLLABORATION
Please include in this section a brief explanation of the activities performed by the participants of this project in conferences, workshops, symposia and other exchange activities. Include summaries and programs of presentations.
Indicate in this section those visits and stays in private labs, academic units, research centers, enterprises, public agencies and so on, that allowed the development of research or other objectives. Include the objectives of the activity and its relevance to the Project. The place visited and the persons contacted should be identified.
Also, include here the short and long visits of researchers from abroad. Please identify the visiting person, his/her specialty, their institution of origin, the objective of the visit, the results (if any).
Mention the long‐term links established between the research team and international institutions (Indicate when there are formal links such as contracts involved).
Third year Our Ring Project has a close interaction with the NSF‐funded project ʺStability of Larsen C Ice Shelf in a warming climateʺ, Principal Investigators Konrad Steffen, University of Colorado at Boulder, and Eric Rignot, University of California at Irvine. Members of our team (José Luis Rodríguez in 2009 and 2010, and Gino Casassa in 2009) have joined field campaigns to Larsen C Ice Shelf together with our US colleagues (see Plate 1). As part of this collaboration José Luis Rodríguez (see V. TRAINING OF STUDENTS, POST‐ GRADUATES AND YOUNG RESEARCHERS) is presently working on his MSc thesis studying the onset of melt in the Antarctic Peninsula and Patagonia by means of passive satellite microwave data. Mr. Rodríguez is currently visiting CU Boulder for a period of 5 months as part of his thesis work (see Annex 1).
The project involved field work at remote places in Antarctica and the acquisition of airborne data that can only be achieved by collaboration with a variety of national and international partners. The basis of the expeditions to Fleming Glacier was created by e Letter of Understanding between The British Antarctic Survey (BAS), Centro de Estudios Cientificos (CECS) and Instituto Antártico Chileno (INACh), defining the logistic support provided by BAS to the project (see Annex 1). Logistics for the operations at Union Glacier (see Plate 1) were facilitated by the private company Antarctic Logistics and Expeditions in view of a long‐term scientific collaboration. As for airborne campaigns, the CECS team is involved in various international initiatives to acquire a wide set of geophysical parameters in the region of the Antarctic Peninsula and beyond. There are cooperation agreements with NASA regarding Operation IceBridge for 2009 and 2010, and an agreement with DTU‐Space, Technical University of Denmark in Copenhagen, Denmark (see Annex 1).
30
Plate 1. Sites covered by the project:; red triangles: case study glaciers of the project, green dots: sites visited by project scientist in the frame of a partner project, orange squares: station used for meteorological and climatological studies.
31 Regarding data and software various international colleagues were consulted to guarantee an optimal analysis. Contacts include John Sonntag, NASA concerning laser scanning data from the HIELO and IceBridge campaigns; Fernando Rodriguez, University of Kansas concerning radio echo sounding data; Hilmar Gudmundsson, BAS; and Reinhard Dietrich, University of Technology Dresden for GPS processing; Jay Zwally for ICESat data, Torborg Haug, University of Oslo for image correlation; and Dana Floricioiu, German Aerospace Center for satellite image acquisition and processing, among others.
Colloquiums and conferences CECS organized the glaciological Conference ʺIce and Climate Change: A View from the Southʺ (VICC 2010). It was held in Valdivia, Chile, 1‐3 February 2010. The objectives of the Conference were to present new results and discuss ongoing cryospheric and climate changes in the Southern Hemisphere and their impacts and consequences on society and the environment. The main focus was glaciology and climatology. A special session was organized by our ring project sponsored by the Bicentennial Science and Technology Programme of CONICYT. During the Conference, several meetings were held with researchers and invited speakers who have a related project such as Neil Ross, Research Associate, University of Edinburgh, UK; Steven Arcone, US Army Cold Regions Research and Engineering Laboratory, USA; Reinhard Dietrich, Technische Universität Dresden, Germany; Rene Forsberg, DTU Space Technical University of Denmark, Denmark; Hilmar Gudmundsson and John Turner, BAS, UK; Pedro Skvarca, Instituto Antártico Argentino, Argentina; Konrad Steffen, CIRES, University of Colorado at Boulder, USA and Jay Zwally, NASA Goddard Space Flight Center, USA. As part of the Conference an APECS (Association of Polar Early Career Scientists) workshop was held for students and early career glacial researchers.
In October, 27 ‐30 2010, CECS and the University Austral de Chile organized the II International PAGES Symposium ʺReconstructing Climate Variations in South America and the Antarctic Peninsula over the last 2000 yearsʺ. The conference brought together scientist from several disciplines such as glaciology, climatology and palynology. The meeting provided an opportunity to meet national and international colleagues and discuss recent results.
Seminars and colloquiums were presented by staff and invited researchers: “Climate Change and the Skeptics” by Jorge Carrasco from DMC, Chile, December 2, 2010; “Mass Changes of the Greenland and Antarctic Ice Sheets in a Changing Climate” by Jay Zwally, NASA Goddard Space Flight Center, USA, November 10, 2010; “Multi‐frequency radio detection instruments for field experiments at polar regions”, Fernando Rodríguez, Center for Remote Sensing of Ice Sheets, University of Kansas, USA, November 10, 2010.
Stays and visits During a visit to Dresden University of Technology, Germany on 10th ‐ 13th May 2010 Anja Wendt discussed the joint analysis of the GPS data acquired during the project and gave a presentation about glacio‐geodetic investigations in the Antarctic Peninsula.
32 Gino Casassa made a 6‐month stay at the Dresden University of Technology (TUD), Germany, between March and October of 2010, as part of a Research Award from the Humboldt Foundation. This stay allowed to strengthen the links between TUD and CECS in the fields of glaciology and geodesy in Antarctica and southern South America. During his stay Gino presented on 7 October 2010 at TUD the seminar ʺMass balance of glaciers and ice caps: a global statusʺ. On 16 June 2010 Gino was invited to Alfred Wegener Institute in Bremerhaven where he presented the seminar ʺThe quest of retrieving paleoclimate records from high‐altitude ice core sites from mid‐latitudes in South America to the Antarctic Peninsulaʺ. Also as part of his stay Gino taught a two week long Hauptseminar in October 2010 11‐22 at the RWTH Aachen University entitled ʺMountain Glaciers and Climate Changeʺ addressed to undergraduate students in Geography. At RWTH he also gave a Colloquium on October 12, 2010 entitled ʺPaleoclimate records from high‐altitude ice core sites from mid‐latitudes in the southern Andesʺ.
In October 2010 Rodrigo Zamora visited Rene Forsberg, Head of Geodynamics at DTU Space Institute, Technical University of Denmark in Copenhagen, Denmark. The main aim of the meetings was the interest for future laser and radar airborne campaigns in the Antarctic Peninsula and the Antarctic interior. The visit also included Jørgen Dall, Associate Professor, National Space Institute, Technical University of Denmark in Lyngby, Denmark in order to present the new CECS radar and become acquainted with the preliminary Danish results of the last Greenland airborne radar data. During his visit he gave the talk “Overview of southern glaciological and climate change research” to the staff of the National Environmental Research Institute, Arhus University, Denmark, on October 8th.
On November 5‐7 2010 Gino Casassa was invited as scientific expert to accompany the President of Chile Mr. Sebastián Piñera and the President of Ecuador Mr. Rafael Correa on a trip to the Antarctic Peninsula starting from Santiago via Punta Arenas, where they would visit both the Chilean Base Frei and the Ecuadorian Base Maldonado. Although the weather did not allow the landing of the Hercules C‐130 aircraft in Antarctica, the Presidential group flew over the South Shetland islands and Gino provided glaciological information throughout the trip.
Second year Research staff meetings During this year we developed several internal meetings of the research group at Centro de Estudios Científicos in order to coordinate field campaigns, assess science advances and schedule publications. Other occasional meetings have included the whole research staff from CECS and associate institution Dirección Meteorológica de Chile (DMC). The last meeting of the year took place in August 2009, where we planned the next campaign, recruitment of students and future papers.
33 Expedition coordination Similarly to the first expedition, planning of the second one involved again several national and international logistics partners, e.g. INACH, Chilean Air Force (FACH) and British Antarctic Survey (BAS) to organize the access to the area under investigation and the field camp itself. Thanks to the direct contact established with Mike Dinn, Operations Manager at BAS, communication between Chilean and British partners could be expedited especially in the definition of the expedition schedule. The proposed airborne laser survey required close coordination with FACH to allow the installation of the instruments in one of their Twin Otters in time for the expedition. All these organisational issues could be resolved just in time for the expedition which started on November 29th 2008.
Stays and visits During a stay at the University of Technology Dresden, Germany in April/May 2009 project director A. Wendt visited Professor Reinhard Dietrich of the Institute of Planetary Geodesy, expert in polar geodesy to discuss details of the GPS analysis of the CGPS station at Fleming. Constructive talks about the laser scanning data collected at Fleming were held with Professor Hand‐Gerd Maas, Institute of Photogrammetry and Remote Sensing, TU Dresden.
Dr. Rivera had a highly productive visit to the UK in July 2009, including an important meeting with David Vaughan, Science Leader of the Physical Science Division at BAS, in order to strengthen our cooperation during the ongoing campaign to Fleming Glacier and thereafter. Other meetings were developed with the Lake Ellsworth Consortium and private company Antarctic Logistics and Expeditions (ALE) enterprise in order to coordiate with further logistical and scientific collaboration in Antarctic investigations in the Ellsworth Mountains that are also related to this project.
There was a close contact with Konrad Steffen, Professor of Geography and Director of CIRES, the Cooperative Institute for Research in Environmental Studies, Boulder, Colorado. He is the PI of the NSF partner project “IPY: Stability of Larsen C Ice Shelf in a Warming Climate” and visited Valdivia from September, 29th to October, 11th 2008 in preparation of the expeditions to Fleming Glacier and Larsen ice Shelf.
Professor Steffen gave a Colloquium ʺGreenland Ice Sheet: Dynamic Response to Global Warmingʺ and held a seminar about Automatic Weather Stations, their sensors and telecommunication. After the expeditions he returned to Valdivia in January to report about the respective field works and discuss first outcomes and continuation of the collaboration. As a result, a co investigator and a postgraduate student of our project (G. Casassa and J.L. Rodríguez) are participating in the upcoming field work on Larsen C in October/November 2009, contemporaneous with our expedition to Fleming Glacier. This activity will further strengthen the link between CECS and CIRES.
34 First year Collaboration with Chilean Armed Forces and foreign institutions The logistic coordination of the expedition was realized by INACH after their acceptance of the requirements of the project (form FORE‐LO 2007) and the editing of a Memorandum of Understanding approved by BAS, INACH and CECS (Annex 1). The expedition started on November, 12 on board the ice breaker “Almirante Viel” of the Chilean Navy taking the expedition party and their equipment in a first leg to the Chilean base station Profesor Julio Escudero (Isla Rey Jorge, 62°12’S, 58°57’W). The subsequent transport to the British base Rothera (Adelaide Island, 67°34’S, 68°07’W) was realized by two Twin Otters (T/O) of the Chilean Air force (FACH). One of the aircrafts stayed in Rothera to support the field activities. At the end of the campaign, the party returned to Rothera, where accommodation, food, office space, the use of the air strip and fuel was provided by BAS during the whole expedition. The members of the expedition returned to Punta Arenas on board a C‐130 aircraft of FACH.
With respect to scientific cooperation there are close links to Dr. Konrad Steffen (U. Colorado en Boulder, USA) y el Dr. Eric Rignot (U. California in Irvine, USA), both investigators of a project sponsored by the National Science Foundation about Larsen C with field work starting in November. This collaboration was confirmed during the 5th International Workshop “Antarctic Peninsula Climate Change (APCC5): Climate Ocean and Life”, June 26, 2008 in Irvine, USA. Plans to cooperate include joint processing of the meteorological data and Chile‐USA exchange of PhD students starting in 2009. A joint field expedition is planned for the season 2009‐2010.
Between September 24 and 26, 2008 a Chilean‐Canadian workshop took place in Ottawa, sponsored by the Chilean embassy in Canada. The result of this meeting is an agreement to develop a scientific collaboration plan between CECS and the University of Ottawa, with its laboratory for cryospheric studies lead by Dr. Luke Copland. This agreement includes the joint analysis of the compiled data and satellite images of Fleming Glacier starting in 2009.
Presentations at international conferences (Abstracts attached in Annex 2)
Wendt, A., F. Bown, A. Rivera, R. Zamora, G. Casassa, C. Bravo, M. Fritsche and R. Dietrich (2011), Ice velocity and ice elevation changes at Fleming Glacier, Antarctic Peninsula, European Geosciences Union General Assembly 2010, Vienna, Austria, 03 – 06 April 2011.
Uribe, J., R. Zamora and A. Rivera (2011), Ice thickness and snow accumulation radar measurements at Union Glacier, West Antarctica, European Geosciences Union General Assembly 2010, Vienna, Austria, 03 – 06 April 2011.
Zamora, R., A. Rivera and J. Uribe (2011) Preliminary results obtained by the most recent field campaign to the Subglacial Lake Ellsworth Area in West Antarctica, European Geosciences Union General Assembly 2010, Vienna, Austria, 03 – 06 April 2011. 35
Wendt, A., F. Bown, A. Rivera, J. Wendt, C. Bravo, R. Zamora, J. Carrasco, J. Quintana, R. Dietrich and M. Fritsche (2010), Climatological and Glaciological Changes in The South of The Antarctic Peninsula: A case study at Fleming Glacier, Wordie Bay, II International Symposium ʺReconstructing Climate Variations in South America and the Antarctic Peninsula over the last 2000 yearsʺ, Valdivia, Chile, 27‐30 October, 2010.
Carrasco, J., J. Quintana (2010), Climate variability an change in The Northern 2 Tip of The Antarctic Peninsula in response to Atmospheric Circulation, II International Symposium ʺReconstructing Climate Variations in South America and the Antarctic Peninsula over the last 2000 yearsʺ, Valdivia, Chile, 27‐30 October, 2010.
Rivera, A., R. Zamora, J. Uribe and M. Sharp (2010), Union Glacier, Ellsworth Mountains: A New Gate For Exploring The Interior Of West Antarctica, SCAR XXX1 Open Science Conference, Buenos Aires, Argentina, July 30 – August 11, 2010.
Wendt, A., F. Bown, A. Rivera, J. Wendt, R. Zamora, C. Bravo, R. Dietrich, M. Fritsche (2010), Dynamics of Fleming Glacier, Antarctic Peninsula: Changes in ice elevation and ice flow velocities, SCAR XXX1 Open Science Conference, Buenos Aires, Argentina, July 30 – August 11, 2010.
Zamora, R., S. Arcone, A. Rivera and J. Uribe (2010), Snow Bridge Characterization by 2d Wave Migration, SCAR XXX1 Open Science Conference, Buenos Aires, Argentina, July 30 – August 11, 2010.
Carrasco, J., J. Quintana, A. Wendt, A. Rivera(2010), Meteorological Analysis of One‐Year in Situ AWS Data Upstream Fleming Glacier, Antarctic Peninsula, SCAR XXX1 Open Science Conference, Buenos Aires, July 30 – August 11, Argentina, 2010.
Quintana, J., J. Carrasco and N. Morandí (2010), Climate Variability in The Northern tip of The Antarctic Peninsula, SCAR XXX1 Open Science Conference, Buenos Aires, Argentina, July 30 – August 11, 2010.
Wendt A., F. Bown, A. Rivera, J. Wendt, R. Zamora, C. Bravo, P. Zenteno, G. Casassa, J. Carrasco and J. Quintana (2010), Glacier dynamics after the disintegration of Wordie Ice Shelf, Antarctic Peninsula, European Geosciences Union General Assembly 2010, Vienna, Austria, 02 – 07 May 2010.
Wendt, A., F. Bown, A. Rivera, J. Wendt, C. Bravo, P. Zenteno, R. Zamora, J. Carrasco, J. Quintana and G. Casassa (2010), Evolution of Wordie Bay glaciers after disintegration of Wordie Ice Shelf, International Glaciological Conference Ice and Climate Change: A View from the South, Valdivia, Chile, 1‐3 February 2010.
36 Carrasco, J., J. Quintana, A. Wendt and A. Rivera (2010), Meteorological analysis at Fleming Glacier, Antarctic Peninsula, derived from one‐year in situ AWS data, International Glaciological Conference Ice and Climate Change: A View from the South, Valdivia, Chile, 1‐3 February 2010.
Quintana, J. and J. Carrasco (2010), Climate variability in the Antarctic Peninsula. International Glaciological Conference Ice and Climate Change: A View from the South, Valdivia, Chile, 1‐3 February 2010.
Bravo, C., A. Rivera, A. Wendt, P. Zenteno, R. Zamora and F. Bown (2010), Recent scientific expeditions to Fleming Glacier, Antarctic Peninsula, International Glaciological Conference Ice and Climate Change: A View from the South, Valdivia, Chile, 1‐3 February 2010.
Carrasco, J., A. Wendt, A. Rivera, J. Quintana (2009). Meteorological Environment at Glacier Fleming, Antarctic Peninsula, Derived from in situ AWS. Abstract published at IAMAS‐IAPSO‐IACS‐Assembly 2009, Montreal, Canada, 19 ‐ 29 July 2009.
Rivera, A., F. Bown, A. Wendt, R. Zamora, J. Wendt, C. Bravo, and M. Rodríguez (2009). In situ accumulation measurements at Fleming Glacier (69ºS), Wordie ice‐shelf embayment, Western Antarctic Peninsula. Poster presentation at IAMAS‐IAPSO‐IACS‐Assembly 2009, Montreal, Canada, 19 ‐ 29 July 2009.
Rivera, A., R. Zamora, C. Rada, J. Walton & S. Proctor (2009). Ice dynamics of Union Glacier in the Ellsworth Mountains, West Antarctica. Poster presentation at International Symposium on Glaciology in the International Polar Year, Newcastle, UK, 27 ‐ 31 July 2009.
Wendt, J., A. Rivera, A. Wendt, F. Bown, R. Zamora, G. Casassa, C. Bravo, and J. Carrasco (2009). Recent field studies of Fleming Glacier, Antarctic Peninsula. Oral presentation at International Symposium on Glaciology in the International Polar Year, Newcastle, UK, 27 ‐ 31 July 2009.
Wendt, A., J. Wendt, F. Bown, A. Rivera, R. Zamora, C. Bravo, and G. Casassa (2009). Ice flow velocities and elevation change at Fleming Glacier, Wordie Ice Shelf, Antarctic Peninsula. Abstract published at Assembly of the European Geophysical Union, Viena, Austria, 19 ‐ 24 April 2009.
Rivera, A., A. Wendt, F. Bown, R. Zamora, J. Wendt, G. Casassa, C. Acuña, 2008, Fleming glacier dynamics after the Wordie Ice shelf collapse, International Workshop on Antarctic Peninsula Climate Change, June 24‐26 2008, UC Irvine, California, USA.
Uribe, P., J. F. Carrasco, P. Aceituno, 2008, Changes in the air temperature regime in the Antarctic Peninsula: associated mechanism, International Workshop on Antarctic Peninsula and Climate Change, June 24‐26 2008, UC Irvine, California, USA. 37
Rivera, A., R. Zamora, R. Mella, F. Bown, A. Wendt, G. Casassa, J. Wendt, 2008, New assessment on the dynamics of Fleming Glacier, Wordie Ice Shelf, Antarctic Peninsula, Joint SCAR‐IASC Open Science Conference, July 8‐11 2008, St Petersburg, Russia.
Uribe, P., J. F. Carrasco, P. Aceituno, 2008, Cambios en el régimen de eventos de temperatura extremas en la Península Antártica, IV Simposio Latinoamericano sobre Investigaciones Antárticas y VII Reunión Chilena de Investigación Antártica, 3‐5 Septiembre 2008, Valparaíso, Chile.
Wendt, A., A. Rivera, F. Bown, G. Casassa, R. Zamora, R. Mella, J. Wendt, J. Carrasco, Estabilidad del sistema plataforma de hielo flotante de Wordie y Glaciar Fleming, Península Antártica, IV Simposio Latinoamericano sobre Investigaciones Antárticas y VII Reunión Chilena de Investigación Antártica, 3‐5 Septiembre 2008, Valparaíso, Chile.
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