Climatic Signals from 76 Shallow Firn Cores in Dronning Maud Land, East

Home , Kohnen Station

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 4 X class copernicus.cls. E T A 1 , and D. Divine 4 , E. Isaksson 1,3 , E. Schlosser 1,2

Institute of Meteorology and Geophysics, Center for Climate and Cryosphere, German Meteorological Service, 63067 Offenbach,Austrian Germany Polar Research Institute, Vienna,Norwegian Austria Polar Institute, Fram Centre, 9296 Tromsø, Norway

S. Altnau in Dronning Maud Land, East Antarctica Climatic signals from 76 shallow ﬁrn cores Correspondence to: S. Altnau ([email protected]) University of Innsbruck, 60202 Innsbruck, Austria 2 3 Date: 11 March 2015 1

with version 2014/09/16 7.15 Copernicus papers of the L Manuscript prepared for The Cryosphere Discuss. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | were inves- O 18 δ , which consider-

O 18 δ

occur mostly in parallel, thus can O 18 δ of both the plateau and the ice shelf cores 2 O 18 δ

increased surface mass balance is still not observed over the entire Antarctic continent. the expected warming combined with a corresponding increase in precipitation and thus only an increase in sea ice extent is observed (Parkinson and Cavalieri, 2012) but also regions is obvious in the Arctic (Stocker et al., 2013), Antarctica behaves differently. Not of the foci of attention. Whereas the enhanced warming that models predict for the polar In the ongoing discussion about climate change, the climate of the polar regions is one 1 Introduction

the plateau, the temporal variations of SMB and partly explain the observed features in the ice shelf cores. regions atmospheric dynamic effects are more important than thermodynamics, while on circulation that result in a changed seasonal distribution of precipitation/accumulation could number of cores was used to calculate stacked records of SMB and and the coastal cores were found. The Comparison with meteorological data from Neumayer Station revealed that for the ice shelf tica. This is not confirmed by the firn core data in our data set. Changes in the atmospheric ditions during the past three decades in Dronning Maud Land, East Antarctica.tection The of large climatic signals. Considerable differences between cores from the interior plateau period, the SMB has a negative trend in the ice shelf cores, but increases on the plateau. a positive trend since the mid-1960s, which is assumed to lead to a cooling of East Antarc- tigated in the first comprehensive study of a set of 76 firn coresably retrieved increased by various the expe- signal-to-noise ratio compared to earlier studies and facilitated theexhibit de- a slight positive trend over the second half of the 20th century. In the corresponding be explained by thermodynamic effects. The Southern Annular Mode (SAM) has exhibited

The spatial and temporal distribution of surface mass balance (SMB) and Abstract Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 were investigated. Additionally, the relationship O 18 δ

In Dronning Maud Land (DML), East Antarctica (Fig. 1), various expeditions have carried Instrumental surface air temperature records from the Antarctic continent are available Close monitoring of changes in both the atmosphere and the cryosphere is necessary in Only the wider Antarctic Peninsula region (including parts of West Antarctica) exhibits

Possible climatic trends in SMB and ratio. The spatial variations were related to topographic and other geographical features. tigated. Calculation of stacked records helped to considerably improve the signal-to-noise variations of stable isotope ratios and SMB derived from a network of 76 cores were inves- study of this unique data set had been carried out. In this study, the spatial and temporal ever, so far only the results of single expeditions have been published; no comprehensive plored DML. Almost 80 cores have been drilled during these expeditions since 1980. How- Community Members, 2006) have increased our knowledge about the hitherto poorly ex- expeditions connected to the European Project for Ice Coring in Antarctica (EPICA) (EPICA frame of different national and international programmes. In particular, the pre-site-survey out glaciological ﬁeld work, including drilling of ﬁrn and ice cores in the past decades in the

cores where annual layers are resolved. water isotope ratio; annual mean SMB can be calculated from density measurements for have to rely on firn and ice cores. Temperature information is derived mainly from the stable limited and most of them are situated at the coast. Thus, to investigate the past climate, we only since the International Geophysical Year (IGY) 1957/58. The number of stations is still point in summer already in the present climate (King and Turner, 1997). regions are highly sensitive to any changes, since the temperatures are close to the melting order to detect early signs of climatic change in East Antarctica. In particular, the coastal rise. in precipitation, and hence increased surface mass balance (SMB), might mitigate sea level (Turner et al., 2005; Monaghan et al., 2006, 2008). This is important because an increase tica, no general warming and increase in precipitation is found in surface observational data ice shelves and accelerated ice flow (Rignot et al., 2013; Rott et al., 2002). For East Antarc- a large increase in air temperature (Bromwich et al., 2013), accompanied by disintegrating Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | E. ◦ one 2 m W and 45 ◦ in N–S direction and km . Further east, the Ekström Ice km 4 . Our study is focused on the western part of DML, 2 km E (see Fig. 1). DML is bounded by various ice shelves of different ◦ and SMB and possible influences of the Southern Annular Mode (SAM) as W and 10 O ◦ 18 δ

in E–W direction and is fed by Jutulstraumen, the largest outlet glacier in DML.

Centred at the Greenwich meridian is the Fimbul Ice Shelf, with an area of 33 000 Shelf is found, which is bounded by two N–S stretching ridges, Søråsen and Halvfarryggen.

frontfjella and, in the frame of EPICA, to Amundsenisen. ical field work was performed along the traverse routes from Ekström Ice Shelf to Heime- Various traverses started at this station since 1986/87 (Miller and Oerter, 1990). Glaciolog- ström Ice Shelf, connected to the German year-round scientific base Georg-von-Neumayer. sporadically until the early 1980s. Systematic data acquisition began in the 1980s on Ek- Norwegian Expedition 1949–1952 (Swithinbank, 1957). Thereafter, DML was only visited the Riiser-Larsen Ice Shelf with a width of about 400 Early glaciological measurements were carried out in our study area by the British–Swedish– sizes. The westernmost ice shelf, for which cores are available for this investigation, is 3 Previous work the higher plateau area, the so-called Amundsenisen. situated. A mountain range to the southeast, Heimefrontfjella, separates Ritscherflya from It covers an areabetween of 15 ca. 2 700 000 of the largest ice200 shelves in DML.South It extends of approximately Riiser-Larsen 100 and Ekström Ice Shelves the lower inland region Ritscherflya is

Dronning Maud Land is situated in East Antarctica approximately between 20 2 Field area

between analysed. the primary mode of atmospheric variability in the extratropical Southern Hemisphere were Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (Schlosser (increasing) in records gener- years O O 18 18 . The study revealed δ δ O 18 δ exhibited a small positive O 18 δ 5 in the area and the role of the Southern Annular Mode (SAM) and O 18 δ deep ice core was retrieved on eastern Fimbul Ice Shelf. The derived m

Divine et al. (2009) used eight firn cores from coastal DML to study the long term changes As part of the Norwegian Antarctic Research Expedition (NARE), Norwegian groups in- The lower inland region Ritscherflya was visited during the field season 1988/89 as part of More recently, several shallow firn cores were retrieved at Søråsen and Halvfarryggen In Austral summers 2009–2011, eight shallow firn cores were retrieved on Fimbul Ice The majority of the extensive EPICA pre-site-survey programme was conducted on the

measurements and modelling (http://fimbul.npolar.no). The Shelf from top to bottom” that combined glaciological measurements with oceanographic and three medium-deep ice cores (see Tab. A1) were drilled on Amundsenisen. The area Shelf during an extensive glaciological field campaign as part of the project “Fimbul Ice high plateau region Amundsenisen. Between 1996 and 1998, a series of shallow firn cores ENSO to the area is stronger in years when the SAM is in its negative phase. the diverging multidecadal trendscoastal in DML. accumulation On shorter (decreasing) sub-decadal and time scales it was found that the teleconnection of trend, whereas a negative trendet al., was 2012; observed Sinisalo in et SMB al., during 2013). the last 30 ENSO (El Niño–Southern Oscillation) in the temporal variability of in accumulation and 20th century (Kaczmarska et al., 2004). accumulation rates showed high temporal variability and a significant negative trend in the 2000/01, a 100 Ice Shelf (e.g. Isaksson and Melvold, 2002 and Melvold et al., 1998). In Austral summer vestigated the spatial and temporal variability of SMB on a traverse that crossed Fimbul et al., 1996). ally showed large spatial and temporal variability (Isaksson and Karlén, 1994a, b; Isaksson the Swedish Antarctic Research Program (SWEDARP). The SMB and we did not omit them from our study.) and are therefore not directly comparable to the other cores. (For the sake of completeness (Fernandoy et al., 2010). However, these cores are strongly influenced by local topography Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | m . Frezzotti et al. (2013) . They stated that SMB , with higher values in the 1 − years a years 2 − . 15 kg m ± years 57 6

Anschütz et al. (2009) presented data from the Norwegian US Scientiﬁc Traverse of East Rotschky et al. (2007) used a special interpolation method to derive a surface accu-

provided a synthesis of Antarctic SMB during the last 800 a positive trend in accumulation for central DML in the past 50 between Kohnen Station and Dome Fuji (along ID2, Figure 1 and further east). They found of accumulation in DML using snow pits, ﬁrn cores and radar data from an IPY traverse earlier measurements. Fujita et al. (2011) investigated the spatial and temporal variability rate at Sites I and M (Isaksson et al., 1999, see also Fig. 1) has not changed since the during which some earlier Norwegian drilling sites were revisited. The mean accumulation Antarctica TASTE-IDEA, through DML from the Norwegian base Troll to the South Pole,

a mesoscale atmospheric model. was confirmed by Schlosser et al. (2008) who compared Rotschky’s results with data from mentioned traverse from Troll to South Pole but found that almost all sites above 3200 with local maxima and minima on the windward and lee-sides of topographic ridges. This markers to investigate century-scale SMB changes in ice cores retrieved during the above- accumulation was found to clearly decrease with elevation and distance from the coast, Divine et al. (2009) and Kaczmarska et al. (2004). Anschütz et al. (2011) used volcanic time mulation map for western DML from firn cores, snow pits, and stake measurements. The since the 1960s, which confirms the results of Fujita et al. (2011) but contradicts those of increase in SMB in coastal regions and over the highest part of the East Antarctic ice divide western part of Amundsenisen. over most of Antarctica does not exhibit an overall clear trend. However, they found a clear altitude show a decrease in SMB in the last 50 Oerter et al. (1999) calculated a mean value of Sommer et al., 2000b, a; Graf et al., 2002; Hofstede et al., 2004; Karlöf et al., 2000, 2005). lation rates for the last millennium (Isaksson et al., 1996; Oerter et al., 1999, 2000, 2004; was found to be characterized by a robust deposition system with nearly constant accumu- Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , two years (Isaksson et al., data. The cores were years O 2 D), supplemented by di- δ 18 ± , δ O 18 δ of different cores are poorly correlated, even 7 O 18 δ -activity measurements (Isaksson and Karlén, 1994a, β , one core almost two millennia. Spatially the dataset rep-

years

rors can considerably reduce the quality of the correlation when no smoothing of the record “blue noise” properties, Fisher et al., 1983), a shift of one or two years due to dating er- SMB series generally demonstrate an increased variance at higher frequencies (so-called to the effects of wind, which particularly affects SMB values. Furthermore, as the annual records from the same drilling location. This is partly due to the large depositional noise due Annual values of SMB and mean annual 4.2 Composite records very irregular and individual. to quantify since it depends not only on accumulation rate, but also on wind scouring that is few decades. For the cores covering centennial scales the dating error is larger, but difficult 1999; Oerter et al., 2000; Schlosser et al., 2012, 2014) for the short cores spanning the last (ECM) (Hammer et al., 1980) and average dating error for single years is given as approximately 2000; Sommer et al., 2000a), and, in the earlier days, electrical conductivity measurements the ice core with a high resolution (Röthlisberger et al., 2000; Sommer et al., 2000b). The electric profiling (DEP) (Wilhelms et al., 1998), continuous flow analysis (CFA) (Oerter et al., b). Continuous flow analysis allowed fast analysis of ammonium, calcium, and sodium along cores reach an age ofresents 1000 the entire Western DML.dated In mainly this using study, we the use seasonality SMB of and stable isotope ratios ( found. The time period covered by the cores ranges from approximately 30 to 200 all firn cores used during this study. In Table A1 detailed information about each core can be field campaigns over a time period of about three decades. Figure 1 shows the location of The available data set consists of 76 shallow firn and ice cores carried out during different 4.1 Shallow firn core data 4 Data and methods Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ; also the three medium-deep cores, years 8 and SMB were calculated. For this calculation, the O 18 δ from this expedition. O 18

Since the cores are situated in different climatic regions (ice shelf, plateau, and transi- The last group contains all 30 cores from the Plateau, on Amundsenisen. The plateau Eight cores retrieved during a recent expedition on Fimbulisen (Schlosser et al., 2012,

all cores of the corresponding group and time period. For SMB, the relative deviation ex- for each core the deviations from the local mean were calculated before averaging over tion zone) with considerable differences in mean precipitation amounts and temperatures, cores cover on average a time period of 200 mean group. completeness and are not used in the stacked records due to data loss on annual SMB and drilled during Austral summer 1988/89 (Isaksson and Karlén, 1994a, b) represent another the cores shown in orange in Fig. 1, along the Ice Divide 1 are given only for the sake of from the south-western corner of the study area, Riiser-Larsen Ice Shelf and Ritscherflya, pangaea.de.) In the discussion of the results we will refer to these sub-groups. Note that the third group. All ice shelf cores together were combined in the fourth group. Seven cores Alfred-Wegener-Institute (AWI), Helmholtz Center for Polar and Marine Research at www. 2014) together with two older cores from the same area (Kaczmarska et al., 2004) form B31–B33) are found here. (The data of the plateau and Ekström cores are provided by care. cores are strongly influenced by local conditions, thus this group has to be considered with on Søråsen and Halvfarryggen (Fernandoy et al., 2010). However, as stated before, these Oerter, 2002a, b). The second group includes these cores plus six more cores situated ten cores drilled in the vicinity of Neumayer Station (Miller and Oerter, 1990; Schlosser and Sect. 4.5.1), stacked records of responding time periods and number of cores. The first set of shallow firn cores comprises is done. In order to reduce depositional noise and enhance thepossible signal-to-noise common ratio time (see period covered. Table 1 shows the different core groups and the cor- cores were divided into several sub-groups, according to geographical region and longest Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | S based on observational ◦ 9 . 2 − m S) at the coast of the ice-covered Weddell Sea, it is not repre- ◦ series with air temperature data, long-term meteorological measure- O 18 δ

west of Kohnen Station already in 1998 and moved to the station in 2007. In coastal

index using the mean pressure difference between 40 and 65 analyses show relatively large errors in the polar regions, Marshall (2003) defined an SAM many other atmospheric fields (Marshall, 2003). Since the pressure fields from global re- tion (EOF) in geopotential height, surface pressure, surface temperature, zonal wind and sure gradient. Thus the positive phase of SAM is characterized by strong, mostly zonal extratropical Southern Hemisphere. It is revealed as the leading empirical orthogonal func- data. A positive (negative) SAM index corresponds to a strong (weak) meridional pres- The Southern Annular Mode (SAM) is the principal mode of atmospheric variability of the 4.4 SAM index the data can be used for comparison with the ice shelf cores (König-Langlo et al., 1998). Fig. 1), built in 1981. The climate of Neumayer is typical for the ice shelves of DML and thus suitable station for our purpose is the German base Neumayer on Ekström Ice Shelf (see proximately 30 to several hundreds kg African base, was moved several times and has no homogenous time series. Thus, the only pressed as a percentage of the mean was used, since accumulation rates range from ap- built in a partly snow-free oasis, which also exhibits very local features. SANAE, the South sentative of the climate of the DML ice shelves. The Russian base Novolazarevskaya was its southern location (75 on the Brunt Ice Shelf in the frame of the International Geophysical Year 1957/58. Due to cal data in DML were provided by the British base Halley, which was established in 1956 Dronning Maud Land, several year-round stations exist. The first operational meteorologi- 1.5 To compare the from the 20th century are available. An automatic weather station (AWS) was installed 4.3 Climatological data ments would be required. For the plateau region of Western Dronning Maud Land, no data Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (1) com- i F individual N and SMB. The O 18 δ ): M ) derived from is determined by multiplying C c F can be estimated (Johnsen et al., i F is shown. c F 10 , ] individual records (VAR M N VAR − C VAR [ of the firn cores, in this study we use the annual SAM index as / ] O /N 18 δ M than for SMB. On the plateau, accumulation rates are considerably lower VAR O − 18 δ C

: mean variance of the individual records : Variance of the composite record VAR C M

with the number of individual cores contained in the composite record. Generally, the = [ In Table 2, for each subgroup (Ice shelf cores, plateau cores, and the 200 year series of : number of individual records contained in the stacked record

i i the plateau cores) the SNVR of the single records (mean of all cores of one group)

N VAR higher for VAR SNVR is higher for the ice shelf cores than for the plateau cores, and, on the plateau also with pared to the corresponding compositeF record

F signal-to-noise variance ratio (SNVR) of a single record records to the mean variance of the

The stacked records are also used to investigate the deposition noise of 1997) by comparing the variance of a stacked record (VAR 4.5.1 Signal-to-noise ratio 4.5 Statistical methods accumulation and http://www.antarctica.ac.uk/met/gjma/sam.html. ther north then the rest of thedefined by continent. (Marshall, 2003). To The examine data the are provided possible by the influence British of Antarctic Survey SAM (BAS) on at a cooling of Antarctica, with the exception of the Antarctic Peninsula, which projects far- moisture and energy between mid and high latitudes (Marshall, 2013) and consequently westerlies with only low amplitudes of planetary waves. This means little exchange of Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | test is used. F , SMB). This will O 18 δ were systematically different in the coastal and SMB. Prior to the procedure the series O 11 O 18 test is essentially defined as ratio of the variance δ 18 δ F , SMB) is entirely due to the predictor (i.e. SAM). The reality O 18 δ in order to obtain reliable results independent on short-term (interan- years in annual snow accumulation we calculated cross correlations between the se- O test. If the original undetrended data were used, this method would assume that the

18 t δ

In order to reveal possible causal links between the atmospheric forcing, regional SMB It turned out that it did not make sense to calculate a stacked record of all available cores

dard trend in the predictand ( opposite (the same) sign. The significance of the correlations is determined using the stan- yield slightly stronger (weaker) correlations if the trends in the composite records are of and ries of SAM, the composite records of possible linear trends in the predictor (i.e. SAM) and the predictand ( year 2000, only data from Fimbul Ice Shelf are available for this study. records. Then these records are detrended, which assumes that there is no link between was chosen as the longest common period covered by a large number of cores. After the these means are determined for the common periods of each combination of the composite To check the statistical significance, the of the data “explained” by the model and the “unexplained variance”. The period 1950–2000 were normalized and detrended for the periods of overlap. First the means and deviation of nual) variability. As a testing procedure for statistically significant trends the

of at least 30 ing speciﬁc procedures and statistical tests: the linear trends are calculated for time periods The statistical signiﬁcance of correlations and trends described in this study is assessed us- 4.5.2 Trends and correlations cores (Oerter et al., 2000) and 16 cores (Graf et al., 2002) was used (see also Sect. 5.2.2). of cores in this study is considerably higher than in earlier studies where a maximum of 12 cores and the plateau cores. However, the signal-to-noise ratio in the two large sub-groups since the temporal changes of SMB and than in the coastal cores. bance of the annual layers, are larger, which leads to higher variance in the plateau cores than in the coastal areas. At the same time, the effects of wind scouring and thus distur- Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ). A rel- . l . ) is found s . 98 . m a . In contrast to 1 = 0 − 2 R km 18.6 ‰ close to Neu- and SMB for cores of − O 18 δ of the cores. Results displayed O 18 δ ) to a maximum of of approximately 8 ‰ . l . s O . 12 18 A strong linear correlation ( δ (Fig. 2a) and SMB (Fig. 2b) for each core. Note . m a l . s O . 18 δ 49.5 ‰ at the south-eastern corner of the study area m a and SMB − O 18 δ values range from and SMB are strongly related to geographical factors such as distance to the O O 18 δ 18 δ

and SMB. However, we note that the mean values of

O Mean Both

18 temperature and precipitation. δ coast and elevation. The inﬂuence of the distance to the coast, continentality, affects both differences between the individual cores could partly be due to temporal changes in annual the plateau. that the time intervals, for which the averages are calculated, are different. Therefore, spatial different age from the same drilling site agree well within the error bounds, particularly on on Amundsenisen (elevation almost 3500 mayer Station at an elevation of 30

between the altitude at thein drilling Fig. location 3 and suggest mean an average decrease in for the entire range of altitudes covered by the cores (approximately 0–3500 Masson-Delmotte et al., 2008), in our study we ﬁnd that the same linear relationship holds cipitation depends on the altitude range because of differences in moisture transport (e.g. other studies, which state that the relationship between altitude and stable isotopes in pre-

from locations close to sea level. As the three-dimensional moisture transport to Antarctica atively large scattering of data points around the ﬁtted line is observed only for the cores

5.1 Spatial distribution of 5 Results

testing procedure via adjustment of the number of degrees of freedom. established. The effects of possible autocorrelation in the series were accounted for in the tative relationship between the variables at the time scale of the whole series cannot be most likely lies somewhere between those two assumptions and a robust causal quanti- Figure 2 shows the mean values of Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) due 90 . = 0 2 R and altitude ( O 18 δ values similar to the Neumayer cores, O 18 δ 13

-elevation relationship since the accumulation at these core sites is strongly inﬂuenced

O Figure 4 shows the dependence of SMB on altitude. A linear correlation between SMB The box plot in Fig. 5 summarizes statistical information on the SMB calculated from the The SMB depends mainly on altitude and continentality and is strongly inﬂuenced by to- The cores from Søråsen and Halvfarryggen were not included in the calculation of the

18 and altitude is found, however, not as strong as between length, the latter corresponding to 1.5 times the interquartile range. Values beyond the found that SMB is generally lower at the lee-side of the ice divides in DML. from the ends of the interquartile ranges to the furthest observations within the whisker the difference is relatively small, our findings confirm the results of Fujita et al. (2011), who distances between the tops and bottoms are the interquartile ranges. Whiskers are drawn Also, SMB is generally lower on the lee-side of ID2 than on the wind-ward side. Even though the median. The tops and bottoms of each box are the 25th and 75th percentiles; the values found here are generally lower than on the wind-ward side of ID2 at similar elevation. stacked records of the corresponding regional sub-groups of cores. The red line indicates This means that the cores along ID1 are all situated on the lee-side of the ridge. The SMB precipitation events, the flow came more often from the N-NE sector than from the NW. to the generally higher spatial variability of the SMB. direction along ID1 is NE. Additionally, Schlosser et al. (2010) showed that during major wind direction. Both Schlosser et al. (2008) and Fujita et al. (2011) note that the main wind divides (dashed lines in Figs. 1 and 2) has an influence on SMB depending on the dominant Apart from the effect of the mountain ranges, the larger scale topography, namely the ice or the mountains clearly leads to deviations from the general altitude dependence of SMB. pographic features. Particularly in the Muehlig–Hofmann-Range (MHG), the local influence cause these anomalies are not yet understood. which implies no significant altitude effect for these sites. The atmospheric processes that

by local topography. They show mean annual δ

et al. (2008) presently cannot be explained physically. is not fully understood yet, the altitude range dependence described by Masson-Delmotte Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | but nine O 18 δ test. t shows little variation. O 18 δ . In the plateau cores this increase 1 (Fig. 7a) and SMB (Fig. 7b) are dis- and SMB for the different composite − O O 18 δ 18 δ of the ice shelf cores increases signiﬁcantly decade O 14 18 δ the smoothed record of years for the regionally stacked records were calculated for different O 18 δ of the plateau cores (Fig. 6e) behaves similar to the ice shelf cores, with the O

18 δ

The stable isotope ratio for Ekström (Fig. 6a and b) and Fimbul (Fig. 6c) Ice Shelves is The linear trends in

largest contribution to this positive trend stems from the period 1950–1980 (see Fig. 6, Ta- is visible, but the positive trend is not statistically signiﬁcant for the considered period. The

(95 % confidence level) by on average 0.18 ‰ played. For the period from 1950 to 2000 The of eleven cross-correlations between the detrended composite records of the given period. For the last 20 the different drilling sites is supported by the calculation of cross-correlations. Only three In Fig. 6, 60 year time series of mean annual Ritscherflya (Fig. 6d) has only a short record, but agrees well with Ekströmexception and Fimbul of for slightly higher values around 1960. The similar temporal variability between 5.2.1 Stacked records of shallow firn cores 1950 to the mid-1960s and the 1980s, whereas the 1970s exhibits values above the mean. 5.2 Temporal variability of regional composite records characterized by values generally lower than the multidecadal average during the periods local topographic influence. the cores on Halvfarryggen and Søråsen, shows extraordinary amounts of SMB due to the in the calculation of the stacked records. whisker length are marked as outliers and plotted as red dots. Again, the group that contains the interannual variability. The grey bars on the panels indicate the number of cores used Fig. 7, linear trends for the composite records of records are presented. Both annual means and 5 year running means are shown to highlight time periods according to the data availability. The detailed results are given in Table A2. In

statistically signiﬁcant at the 95 % conﬁdence level according to Student’s cross-correlations between the smoothed records (5 year running mean) are found to be 1 Discussion Paper− | Discussion Paper | Discussion Paper | Discussion Paper | decade 2 − 4.2 %) − kg m ( increased 2 − O 4.30 (Fig. 8a) and 18 − δ O kg m 18 δ 2.4 − ). The detailed results of the SMB 1 − decade 2 15 − kg m ) and from 0.64 to 1.7 (SMB) (see Table 2). Figure 8 O 7.25 18 − δ and SMB around the mean (Graf et al., 2002). Our study covers chronology from Amundsenisen, this period is characterized by O

18 and SMB generally decrease with 0.23 ‰ and δ O

years 18 δ

The analysis of the stacked SMB series reveals a generally less uniform picture of tem-

19th century, the S100 and B04 (see Fig. 1, Table A1) for the time period 1800–1997. In the first half of the illustrates the 11 yearSMB running (Fig. means 8b) of the for composite the time plateau series cores of and for the two intermediate-depth ice shelf cores, which is statistically significant only on Ekström Ice Shelf with a magnitude of observed (significant at the 90 % confidence level), the ice shelves show a negative trend, poral changes in the regional SMB: whereas on the plateau, a positive trend in SMB is series). from Ritscherflya were excluded for the trend calculation due to the shortness of the data ble A2), for which also the plateau cores exhibit a significantly positive trend. (The cores strong fluctuations of variance ratio from 2.2 to 4.1 ( in DML. In a 1000 - Graf et al. (2002). Using a composite of all available cores increases the signal-to-noise widely seen in the Northern Hemisphere between 1650 and 1850 is not clearly present This has so far been done with only a subset of the cores by Oerter et al. (1999, 2000) and 70s on, a stronger increase in SMB is observed. The Little Ice Age (LIA), a colder period For Amundsenisen, additional composite records that extend back to 1800 were calculated. Thereafter, small negative deviations occur only during brief time periods, and from the late posite record of all ice shelves ( 5.2.2 Intermediate-depth ice cores the 19th century, followed by a longer negative period from approximately 1830 to 1910. for the studied period. For 1980–2009, the negative trend becomestrend significant analysis for are the presented com- in Table A3. per decade, respectively. Afterin a the minimum 20th around century. 1850 The and SMB again shows 1885, positive deviations from the mean in the first part of Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O 18 δ , the picture is less uniform: periods where O 16 and SMB 18 δ O 18 and SMB was considered. It has to be kept in mind, and SMB due to the linear relationship between δ and SMB O O O 18 18 18 δ δ δ and SMB show fairly similar long-term temporal variations. For are in phase vary with anti-phase periods. Note that the ice shelf ). Also for the shorter time period 1950–2000, both stable isotope O O 59 . 18 18 δ δ (Fig. 9a) and annual SMB (Fig. 9b) from all ice shelf cores together with = 0 air temperature and surface pressure at Neumayer Station. The compos- r O for this period, whereas SMB has been decreasing. Generally, a positive m 18 δ series the smoothed records are positively correlated (statistically significant O of the common period, the SMB inferred from the coastal cores and plateau 18 δ years years

The two ice shelf cores (B04 and S100) show a fairly different picture. Apart from the

5.3 Possible influence of SAM on more important for the coastal cores than in the interior and will be discussed in Sect. 6. apart from this thermodynamic influence, there are dynamic influences, which seem to be mean annual This means that warmer (colder) air is usually associated to higher (lower) SMB. However, a possible influence of SAM on Hemisphere climate variability (Marshall, 2007). Figure 9 displays the stacked record of and air temperature and the temperature dependence of the saturation vapour pressure. In order to investigate the influence of atmospheric dynamics onthough, our that results, SAM as a typically first explains step, only approximately 35 % of the extratropical Southern annual mean 2 at the 95 % level, trends of On Amundsenisen, the 200 ratio and SMB show positive trends. On the contrary, the ice shelf cores exhibit positive 5.2.3 Relationship between multidecadal scales, although they were drilled on two different ice shelves. “composite record” consists of only two cores. However, they show a similar variability at correlation is assumed between

coastal and plateau ﬁrst 40 cores exhibit almost opposite trends. For

century (seen in Fig. 8) cannot clearly be related to the LIA in the Northern Hemisphere. only the second half of the LIA and the relatively cool period in the second half of the 19th Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | exhibits a weak, but statistically O 18 δ C, ◦ 16 for the period 1950–2009. (Note that for the ) and SMB. This was the ﬁrst comprehensive − 17 1 O − 18 δ decade . 74 . 0 − = r only cores from Fimbul Ice Shelf contribute to the stacked record). Both years ), which would be expected, however, there is no trend towards lower pressure 56

. 0

−

= The annual SAM index shows a signiﬁcant positive trend that started around 1965. Gen-

trends could be analysed with a higher reliability than previously. compared to earlier investigations of subsets of the firn core data. Thus possible climatic reduced depositional noise and enhanced the signal-to-noise variance ratio considerably study of this data set from coastal, transitional and interior DML. The large number of cores coefficient increases to during the considered period. When the time series of SAM is detrended, the correlation variability of water stable isotope ratios ( 76 shallow firn cores from DML were analysed in order to assess the spatial and temporal most recent 9 6 Discussion and conclusion

( pressure at Neumayer is statistically significantly negatively correlated with the SAM index features are not in line with the anticipated effect of a more positive SAM index. Surface varies slightly around the long-term mean of ional heat exchange (Marshall, 2013). However, whereas Neumayer air temperature only stronger westerlies lead to lower temperatures in East Antarctica due to the reduced merid- a higher SAM index is mainly caused by lower pressure around Antarctica; the consequently significant positive trend of 0.15 ‰ with the SAM index in East Antarctica since the larger pressure difference that leads to erally, both surface pressure and air temperature are supposed to be negatively correlated of the continent is similarly influenced by changes in general atmospheric flow patterns. than the interior plateau. On larger time scales, i.e. glacial–interglacial changes, the interior present climate they seem to be more influenced by changes in atmospheric flow conditions systems in the circumpolar vortex. Therefore, according to our findings in Sect. 5.2.3, in the ite record of the ice shelves is chosen since these regions are influenced by low-pressure Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | values in the O 18 of an ice/firn core, δ O 18 δ 18 in the second half of the 19th century, the corre- O 18 δ and SMB derived from the plateau cores are distinctly dif- O . Precipitation and thus SMB in the coastal areas are depen- 18 O δ 18 δ

For the broad relative maximum of Precipitation at the plateau occurs in form of diamond dust on most days of the year. It The temporal variations of

mulation would have decreased even stronger than summer accumulation. A combination sponding SMB is still generally lower than the average. This would mean that winter accu- depending on which seasons were preferred (Schlosser, 1999; Noone et al., 1999).

accumulation during a colder period could lead to higher annual mean should be discussed generally. For instance, a considerably lower ratio of winter/summer influence on stable water isotope ratios and SMB is not restricted to the coastal areas and bring up to 50% of the annual accumulation (Schlosser et al., 2010). Therefore the dynamic lead to a positive or negative bias in the temperatures derived from orographic lifting of the air mass. These snowfall events, even though they are rare, can paratively small. Thus a change in precipitation (and hence accumulation) seasonality could connected to advection of warm air due to amplification of Rossby waves and consequent firn core because the contribution of the colder season to the annual mean would be com- However, it was found that also real snowfall is observed in the interior of the continent. It is consists of very fine ice crystals that form due to radiative cooling in almost saturated air. et al., 2010). of the trough and the type of the atmospheric circulation (zonal/meridional flow)(Schlosser tation seasonality as well as precipitation amounts, depending on the strength and location synoptic activity in and north of the circumpolar trough can have a strong impact on precipi- frontal systems of cyclones moving from west to east north of the coast. Changes in the dent on the synoptic activity in the circumpolar trough. Usually precipitation is connected to dance with the changes in of precipitation. On the contrary, the SMB of the coastal cores does not change in accor- mean higher saturation vapour pressure, thus more moisture and potentially larger amounts thermodynamic influences, namely the saturation vapour pressure. Higher temperatures to the stable isotope ratio, thus seems to be mainly affected by temperature-dependent, ferent from those of the coastal cores. The SMB on the inland plateau is positively correlated Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | for the ice shelf O 18 δ 19 values than in a period with negative SAM index, even O 18 δ , a positive SAM means a generally more local moisture source, thus less iso- O 18

Apart from all factors that affect precipitation it should be kept in mind that also post- Another important factor that inﬂuences the stable isotope ratio of Antarctic precipitation For The lack of correlation between SAM index, air temperature and

mentioned redistribution of snow due to wind influence, the sublimation-deposition cycle depositional processes alter the stable isotope ratio of the snow. Additional to the afore- on the given time scale for the presented data set. Cavalieri, 2012), thus the influence of sea ice on the ice core properties cannot be discussed sea ice does not show any systematic differences in relation to SAM (e.g. Parkinson and above the water/ice surface (Noone and Simmonds, 2004). However, in the DML region energy balance of the ocean, thus changing temperature and moisture amounts in the air is sea ice. It determines the availability of water vapor and has a strong influence on the

topic fractionation and higher though the temperature might have been relatively low. dynamic and thermodynamic influences. would not necessarily lead to a higher SMB. Therefore low SMB values could be due to both than in a period with negative SAM index. Thus even a higher number of precipitation events of heat and moisture would mean that precipitation amounts for single events were smaller of precipitation events. Apart from that, a more zonal flow and less meridional exchange and faster moving cyclones alone could lead to less accumulation due to reduced duration are always influenced by the synoptic activity in the circumpolar trough. Higher wind speeds cyclone activity do not necessarily have to lead to higher accumulation. The coastal areas its seasonality certainly play an important role here. Stronger westerlies and more intense regions is highly interesting. The reasons are not yet entirely clear. Variations in SMB and

combined with modelling studies are necessary to shed more light on this problem. Recent data alone are not sufficient to confirm this hypothesis. More detailed investigations cation of the sea ice edge and thus of the frontal zone) could explain the observed features. effects (less precipitation events in winter due to e.g. a more zonal flow or more northern lo- of the thermodynamic effect (generally lower SMB due to lower temperature) and dynamic Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , a full O 18 δ and SMB derived from the firn cores O 18 δ 20 values. Diffusion in the pore space due to temperature gradients tends O 18 δ

We conclude that, in the last two centuries, conditions in the interior DML have been fairly

water vapour combined with high-resolution atmospheric modelling would be desirable. tionally to firn cores and snow samples, continuous monitoring of the stable isotope ratio of cannot be fully explained yet.understanding In of order the to three-dimensional understand moisture the transport temporal to variability of Antarctica is required. Addi- eas, more complex processes are at work and the stable and only weakly influenced by changes in atmospheric dynamics. In the coastal ar- thought. with the atmospheric layer just above the snow surface is more important than previously can change the al., 2014; Hoshina et al., 2014) have shown that the interaction of the air in the pore space to smooth the seasonal variations (Johnsen , 1977). Most recent studies (Steen-Larsen et Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 21 variability in Antarctic coastal ice cores, J. Geophys. Res., 114, O 18 δ We are grateful to all members of the various expeditions, who did the field

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Wilhelms, F., Kipfstuhl, J., Miller, H., Heinloth, K., and Firestone, J.: Precise dielectric profiling of ice Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) N 28 ) 1950–2006 16 R RegionFimbul Ice ShelfEkström Ice ShelfEkström Ice Shelf ( Ice Shelves 1950–2009 1950–2001RitscherflyaPlateau Period Number of Cores 1950–2009 9 ( 7 1970–1988 1950–1997 18 6 30 Time periods and number of contributing cores for the composite records for western DML. ryggen. ström (R)” refers to all cores from Ekström Ice Shelf plus the adjacent ridges Søråsen and Halvfar- Table 1. ”Ice Shelves” corresponds to all cores from Fimbul, Ekström and Riiser-Larsen Ice Shelves. ”Ek- Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) (see N )( i F with the number i F c F i F 0.35 4.2 0.09 2.7 0.14 4.1 O O O 18 18 18 is determined by multiplying δ δ δ SMB 0.39SMB 4.7 0.07 2.1 c and SMB in the individual records ( F 29 O ). c 18 F δ Plateau Plateau (200a) SMB 0.06 1.7 Ice shelves Composite record Parameter Signal-to noise variance ratio of Eq. 1) compared to theof composite individual records cores ( contained in the composite record. Table 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − a 2 − SMB kg m H 2 155 329 Fernandoy et al. (2010) 353355 61 61342352 Oerter et al. (2000) 345 Oerter et al. 41 (2000) 369 59352 91 Oerter et al. 53 (1999) Oerter et al. 71 (1999) Oerter et al. (1999) Oerter et al. (1999) Oerter et al. (1999) 187 352146176 Schlosser (1999) 183 335185 294186 295 Oerter et195 al. (1999) 266 Oerter et198 al. (1999) 222 Oerter et al. (1999) 277 Oerter et al. (1999) 371 Oerter et al. (1999) Oerter et al. (1999) Oerter et al. (1999) δ − − − − − − − − − − − − − − − − O 18 21.222.124.425.927.030.6 38130.6 414 34345.0 Isaksson and Karlén (1994b) 32245.1 Isaksson and Karlén (1994b) 25846.9 Isaksson and Karlén (1994b) 28344.9 Isaksson and Karlén (1994b) 31843.9 Isaksson and Karlén (1994b) 45.3 Isaksson and Karlén (1994b) 43.7 Isaksson and Karlén (1994b) 47.1 4544.7 77 Oerter et al. (2000) Isaksson et al. (1996) 19.723.721.922.520.822.0 29522.1 33020.5 298 Schlosser et23.5 al. (2012) 282 Schlosser et al. (2012) 296 Schlosser et al. (2012) 314 Schlosser et al. (2014) 339 Schlosser et al. (2014) 271 Schlosser et al. (2012) 268 Schlosser et al. (2014) Isaksson et al. (1999) Kaczmarska et al. (2004) 20.7 20.720.118.6 23.0 24.0 1252 77224.9 Fernandoy et al. (2010) 25.4 Fernandoy et al.19.6 (2010) 20.420.1 353 1123 Schlosser (1999) Fernandoy et al. (2010) 20.324.222.8 1104 558 Fernandoy 489 et al. (2010) Fernandoy et al. (2010) Fernandoy et al. (2010) δ − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − 30 m m ‰ ‰ 70 9.10 1979–1986 WWW 70 300W 700W 800W 1200 10 10 1200 10E 1976–1987 10E 1974–1988 10 2882 1973–1988 10 3160W 1970–1988 1971–1988 W 148.8 2817 1973–1988 E 3014 71.1E 167–1997 2843E 10.1 3161 1000–1997 10.8 2882 1895–1995 11.6 1919–1995 11.7 11.2 1941–1996 1905–1996 1930–1996 W 30 10W 1975–1988 2669 91.6 1000–1997 WWW 57E 66E 82W 58 10W 48 16.7E 75 14.5E 53 1993–2009 1983–2009 10.7 63 1983–2009 11 48 17.5 1991–2009 20 1992–2009 1981–2009 10 100 1995–2009 1956–1996 1737–1996 W 28 51.7 1892–1981 WW 690 655WW 58 84W 78.5W 75 1960–2006 298W 1935–2006 9.5 559W 788W 5.1W 1971–1986 28 9 600 9.5 28 1969-1986 10 1967-1986 1969-1986 10 16 1973–1986 13.2 1975–1988 1995–2001 1980–2001 WW 630W 539 760 14 43 36 1996–2001 1959–2006 1962–2006 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 E 2900 20.1 1865–1991 W 39 10 1972–1986 0 0 35.39 33.45 25.61 12.61 00.99 43.35 00.42 29.91 00 33.00 55.12 57.65 13.05 00.42 38.73 25.82 36.72 24.12 02.46 00.60 48.00 06.54 48.00 48.66 48.00 22.00 41.93 55.00 22 31.23 20.83 36.68 43.48 49.42 15.15 47.63 15.22 51.64 40.02 33.50 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ S 14 S 12 S 12 S 12 S 12 S 11 S 00 S 06 S 02 S 03 S 01 S 07 S 00 S 16 S 03 S 00 S 00 S 00 S 02 S 04 S 00 S 00 S 04 S 04 S 08 S 06 S 09 S 08 S 08 S 08 S 08 S 08 S 08 S 06 S 08 S 09 S 06 S 09 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 S 02 S 08 0 0 45.72 27.39 35.63 48.95 00.84 21.08 00.14 10.02 00 51.30 58.10 29.95 23.94 00.14 39.25 34.89 49.38 54.12 32.70 24.60 13.98 18.96 18.60 14.50 13.98 37.00 09.73 24.50 37 56.90 24.10 49.92 59.00 09.73 39.52 12.86 39.34 27.43 34.08 03.84 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ 75 75 75 74 74 74 74 75 74 70 70 5 5 5 5 5 Location (latitude, longitude, elevation), total depth, time period and annual mean values D and SMB for all cores in western Dronning Maud Land (see Fig. 1). δ 2 1 , 5 5 5 O 20 100 C(89)D(89)E(89)F(89) 72 G(89) 73 H(89) 73 73 B32 74 B33 74 EPICA FB96DML01 FB96DML02 FB97DML03 FB97DML04 FB97DML05 B31 A(89) 72 G3G4G5G8LP1 69 M2 70 S32 70 S 70 S 70 70 70 Core label LatitudeB04 Longitude Elevation Total depth 70 Period Mean of Parameters References B38B39E002E040E70W 71 E090 71 70 E143 70 E160E180 71 FB0189 71 FB0201 71 FB0202 72 70 71 70 FB0203FB0702FB0704 71 71 72 18 δ Table A1. of Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − a 2 − SMB kg m H 2 346 88 Oerter et al. (2000) 343 68375369 Oerter et al. 58 (2000) 40 Oerter et al. (2000) 339 Oerter et al. (2000) 63 Oerter et al. (2000) 304 206 Oerter et al. (2000) 386 47 Oerter et al. (1999) 379 45 Oerter et al. (1999) 367 60 Oerter et al. (1999) 348 57 Oerter et al. (1999) 369 50 Oerter et al. (1999) δ − − − − − − − − − − − O 18 44.1 43.7 44.8 63 Oerter et al. (2000) 44.6 48 Oerter et al. (2000) 42.6 50 Oerter et al. (2000) 38.5 32.5 129 Oerter et al. (2000) 49.3 48.6 44.946.348.049.526.7 53 44 Isaksson et al. 41 (1999) 45 Isaksson et 244 al. (1999) Isaksson et al. (1999) Isaksson et al. Isaksson (1999) et al. (1999) 47.0 33.438.440.541.2 123 116 59 Isaksson et al. (1999) Isaksson et al. (1999) 30 Isaksson et al. (1999) Isaksson et al. (1999) 44.5 33.4 171 Isaksson et al. (1999) 47.3 33.3 135 Isaksson et al. (1999) 46.0 8646.1 Oerter et al. (2000) Oerter et al. (2000) 47.9 47.1 46.145.544.143.443.1 50 64 53 Oerter et al. 47 (2000) Oerter et al. (2000) Oerter et al. (2000) Oerter et al. (2000) δ − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − − 31 and accumulation were adopted from Isaksson et al. (1999). O 18 δ m m ‰ ‰ EE 3268E 3341E 3406E 3453 800 9 1965–1996 15.2 1965–1996 1962–1996 1974–1996 1965–1996 52 Isaksson et al. (1999) EE 3074 3174 1965–1996 1965–1996 46 Isaksson et al. (1999) E 2980 32.2 1801–1997 E 3160 23.5 1801–1997 E 2843EE 32.9 3160 3100 1801–1997 16.9 21.3W 1810–1997 3014 1800–1997 21 1801–1997 EW 2970W 2840W 2740 2680 25.8 21.7 19.7 1801–1997 24.5 1801–1997 1800–1997 1800–1997 E 2860 26.8 1801–1997 E 2880 29.6 1758–1997 W 2840 20 1800–1997 W 2630 20.6 1801–1997 W 2600 29.3 1921–1997 W 1439 26.4 1881–1997 E 3349 11.3 1900–1996 E 3145 11.1 1897–1996 EE 2610E 2751E 2840 2929 10.1 1976–1996 1965–1996 1965–1996 1965–1996 24 Isaksson et al. (1999) E 2962 11.4 1919–1996 E 2400 1965–1996 W 2669 12.1 1908–1996 E 2044 12.2 1971–1996 E 1520 13.3 1971–1996 E 3246 11.8 1899–1996 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00.10 57.65 59.99 02.17 59.70 00.00 29.82 44.50 21.00 29.50 06.22 47.45 00.10 35.83 12.78 00.00 39.77 21.08 02.65 27.63 56.43 16.97 53.47 25.82 10.51 05.00 00.32 30.00 30.10 00.02 55.12 30.06 29.67 29.78 29.90 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ west of Ekström-Traverse 1987. The location is marked on page 187 in Miller and Oerter (1990). S 11 S 12 S 15 S 04 S 09 S 05 S 06 S 07 S 04 S 06 S 01 S 06 S 05 S 03 S 02 S 01 S 04 S 06 S 00 S 00 S 00 S 06 S 08 S 09 S 11 S 07 S 03 S 03 S 04 S 03 S 02 S 03 S 03 S 03 S 08 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 km 40.03 05.04 29.95 45.04 59.82 10.04 15.02 51.10 12.30 13.00 21.50 38.50 59.50 11.50 02.50 56.00 02.50 30.50 40.50 51.50 23.50 43.50 45.17 15.50 34.89 08.01 54.00 00.04 15.05 10.04 58.10 05.02 56.95 00.00 00.04 ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ 74 74 74 71 74 73 73 74 75 74 75 75 74 75 74 75 75 74 74 75 75 74 74 75 75 73 72 72 72 75 72 74 72 71 75 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Continued. 4 4 4 4 4 4 3 3 3 15 4 3 4 Core E70W was drilled 19 The core was drilled inFor an these area, cores which no has SMBFor been data these identified were cores as available. no a Thus data potential the were deep-drilling mean available. site values Thus of by the SMB the mean (1965–96) EPICA values were research of adopted program (Isaksson from et Isaksson al., et 1996). al. (1999). The data of the plateau and Ekström cores are provided by Alfred-Wegener Institute (AWI) at www.pangaea.de. 4 J K L M S G D E F H I FB9810 FB9811 FB9809 FB9812 FB9813 SS9813 FB9814 FB9815 FB9816 FB9817 FB9808 FB9807 FB9805 FB9804 FB9803 FB9802 FB97DML10 FB97DML09 FB97DML08 C FB97DML07 B A Core label LatitudeFB97DML06 Longitude Elevation Total depth Period Mean of Parameters References 3 4 1 2 5 Table A1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ∗ 16 15 . . 24 . 0 0 0 ± ± ± 27 28 16 . . . 0 0 15 1813 0 . . . 27 15 . . 0 0 0 0 0 ± ± ± ± ± 10 07 14 . . . 06 01 . . 0 0 0 . Significant trends according − − − O 18 δ 21 29 0 15 10 0 . . . . 18 . 0 0 0 0 0 ± ± ± ± ± 02 21 09 07 . . . . 20 . 0 0 0 0 0 − − − − 15 15 22 30 09 . . . . . 32 0 0 0 0 0 ± ± ± ± ± 62 67 53 70 32 . . . . . 0 0 0 ] for the stacked records of 1 09 0 1408 0 07 06 . . . . . − 0 0 0 0 0 ± ± ± ± ± 08 18 27 19 18 . . . . . decade 0 1950–2000 1950–1980 1960–1990 1970–2000 1980–2009 0 0 0 0 ) R Linear trends [‰ test on the 95 % (bold and underlined) and 90 % confidence level (bold) are highlighted. The Trend period ends 2006. Ekström Ice Shelf ( Ice Shelves Fimbul Ice Shelf Ekström Ice Shelf Plateau ∗ F standard deviation of the slope is also given. to Table A2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ∗ 69 10 . 50 . . 3 4 4 ± ± ± 26 25 83 . . . 6 7 3 − − − 09 46 87 . . . 35 12 . . 4 4 2 1 3 ± ± ± ± ± 50 70 95 . . . 07 23 . 2 4 0 . 1 5 − − − 62 66 . . 14 34 50 2 . . . 3 5 3 1 ± ± ± ± ± 81 41 . . 81 58 44 . . . 3 4 − − 53 5 28 2 54 0 . . . 79 04 . 33 . 6 4 1 2 4 ± ± ± ± ± 95 89 59 . . . 78 17 . 5 2 0 . ] for the stacked records of SMB. Significant trends accord- 0 5 1 − − − − 94 61 77 . . . 42 79 1 . . 2 1 1 0 decade ± ± ± 2 ± ± − 41 17 30 . . . 39 43 . . 2 2 4 1 0 1950–2000 1950–1980 1960–1990 1970–2000 1980–2009 − − − kg m ) R Linear trends [ test on the 95 % (bold and underlined) and 90 % confidence level (bold) are highlighted. F Trend period ends 2006. Fimbul Ice Shelf Ekström Ice Shelf ( Ekström Ice Shelf Ice Shelves Plateau ∗ Table A3. ing to The standard deviation of the slope is also given.

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

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° W 5 5 W 2 5 2 0 0 (b) (a) Mean annual are arranged in the same way as in Fig. 1 (NA: not available). (b) Figure 2. (a) all firn and ice cores (NA: not available). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 8 . 20 − ] m [ ALT · 008 . 0 − 98) . = 36 O = 0 18 2 δ R Altitude [m] ( - ya fl ömisen plotted vs. core site altitude. Solid black lines show the respective O 18 Ekstr Plateau Fimbulisen Ice divide Ritscher δ

0 500 1000 1500 2000 2500 3000 3500

[ O ]

-15 -20 -25 / -30 -35 -40 -45 -50 δ 18 o Core average and symbols. linear fits to the data. Cores from different regions of the study area are shown in different colours Figure 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 9 . ] + 326 m [ ALT · 089 . 0 − 90) = . 37 = 0 2 Altitude [m] SMB R ( - ya fl ömisen Ekstr Plateau Fimbulisen Ice divide Ritscher 0 500 1000 1500 2000 2500 3000 3500 0

100 200 400 300 500 M [kgm SMB ]

2 − Core average SMB plotted vs. core site altitude. Solid black lines show the respective and symbols. linear ﬁt to the data. Cores from different regions of the study area are shown in different colours Figure 4.

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

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1 − 2 − Box plot for the SMB of the stacked records. The red line indicates the median. The dots. the interquartile range. Values beyond the whisker length are marked as outliers and plotted as red ranges to the furthest observations within the whisker length, the latter corresponding to 1.5 times Figure 5. and bottoms are the interquartile ranges. Whiskers are drawn from the ends of the interquartile tops and bottoms of each box are the 25th and 75th percentiles; the distances between the tops Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

M [%] SMB M [%] SMB 25 0 −25 −50 −75 −100 100 75 50 0 −25 −50 −75 −100 100 75 50 25 2010 2000 1990 1980 Year 1970 1960

0 5 0 1950

10 20 10

N N 32 39 20 10 0 10 5 0 2010 2000 1990 1980 Year 1970 ¨ om Ice Shelf (R) ¨ om Ice Shelf 1960 (b) Ekstr (a) Ekstr

4 3 2 1 0 2 1 0 4 3

1950

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oo oo

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o o 18 18 Figure 6. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

M [%] SMB M [%] SMB 100 75 50 25 0 −25 −50 −75 −100 100 75 50 25 0 −25 −50 −75 −100 2010 2000 1990 1980 Year 1970 1960 5 0 5 0 1950 10 10

40 N N 33 10 5 0 10 5 0 2010 2000 1990 1980 Year ya ﬂ 1970 1960 (d) Ritscher (c) Fimbul Ice Shelf

0 4 3 2 1 0 4 3 2 1

1950

−2 −3 −4 −1 −2 −3 −4 −1

oo oo

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δ δ

o o 18 18 Figure 6. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

M [%] SMB M [%] SMB 0 −25 −50 50 25 0 −25 −50 50 25 2010 2000 1990 1980 Year 1970 1960

0 0 1950

30 15 20 10

N N 41 34 30 15 0 20 10 0 2010 2000 1990 1980 Year 1970 1960 (f) Plateau (e) Ice shelves

1 0 4 3 2 1 0 4 3 2

1950

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oo oo

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o o 18 18 Figure 6. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (c) year

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | M [%] SMB 50 25 0 −25 −50 2010 2000 1990 Total. Also shown is a 5 (g) 1980 Year ] (left) and the SMB as deviation 1970 oo / o 1960 Ekström Ice Shelf and adjacent ridges, Plateau and ¨ om Ice Shelf and adjacent ridges, (c) Fimbul (f) (b)

0 1950

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4 3 2 1 0

1950

−1 −2 −3 −4 oo ] / [ O

o 18 Composite records of Fig. 6. from the mean [%] (right): Ice (a) Shelf, Ekstr (d) Ritscherﬂya, average(e) (thickShelf red and ice black (all), lines).posite(f) The records. grayPlateau The bars and shaded indicate the areas (h) number representfromTotal. of time Also mean cores periods . that shown with contribute positive is to (red) a the and com- negative 5 (blue) year deviations moving (blue) deviations from mean. to the composite records. The shaded areas represent time periods with positive (red) and negative moving average (thick red and black lines). The gray bars indicate the number of cores that contribute Figure 6. from the mean [%]Fimbul Ice (right): Shelf, Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

test are

M [kgm SMB dec ]

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0 0

oo [ O / dec ]

o 18 1 Linear trends for composite records of − Statistically significant trends on the(orange) 95 bars. % (90 Trends %) with confidencestandard lower level deviation according significance of to the are slope. coloured in grey. The black error bars represent the Fig. 7. bars represent the standard deviation of the slope. shown as red (orange) bars. Trends with lower significance are coloured in grey. The black error 2000. Statistically significant trends on the 95 % (90 %) confidence level according to Figure 7. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | M [%] SMB ] and 50 25 0 −25 −50 oo / o 2000 1960 1920 as deviation from the mean [‰] O 1880 18 δ as deviation from the mean [ (a) O 18 1840 δ (b) 0 1800 30 15

37 N 44 30 15 0 2000 moving average) of: 1960 year 1920 1880 1840 Composite records (11 year moving average) of: (a) (a)

3 2 1 0 4

1800

−1 −2 −3 −4

] [ O oo / δ

o 18 (b) SMB as deviation fromlast the two mean centuries. [%] for Theof the grey the plateau bars plateau. (solid indicate The line) ice the and(red) shelf number coastal and record region negative of consists (blue) (dashed) cores only deviations for of from that the the S100 contribute mean. and to B04. the Shading: composite Time periods record with positive Fig. 8. Composite records (11 SMB as deviation from the mean [%] for the plateau (solid line) and coastal region (dashed) (b) Figure 8. and with positive (red) and negative (blue) deviations from the mean. record of the plateau. The ice shelf record consists only of S100 and B04. Shading: time periods for the last two centuries. The grey bars indicate the number of cores that contribute to the composite Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Mean annual (b)

(black), annual mean

] [ Pa hP p ] C [ T ◦ 985 980 1000 995 990 −14 −15 −16 −17 −18 −19 −20 −21 −22 2010 Ice Shelves 2000 1990 of composite record Ice Shelves (black), annual 45 38 1980 O Year 18 of composite record δ O 1970 18 δ 1960 (b) (a) (black), annual mean pressure of Neumayer station (blue), and annual 0 1 0 4 3 2 1950

25 50

−1 −2 −3 −4

−25 −50 oo

A index SAM | ] / [ O

10) ( | [%] A index SAM SMB

δ · o 18 Ice Shelves Time series of mean annual (a) Time series of mean annual

mean air temperature of Neumayer station (red) and annual SAM index (green). and annual SAM index (green). Bold lines: 5 year moving average. SMB of composite record Ice Shelves (black), annual mean pressure of Neumayer station (blue), Figure 9. (a)

Fig. 9. composite record air temperature of Neumayer station (red) andSAM annual index (green). SAM Bold index lines: (green). 5-year moving(b) average Mean annual SMB of