North Atlantic Oscillation – Concepts and Studies
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Modeling Global Sea Ice with a Thickness and Enthalpy Distribution Model in Generalized Curvilinear Coordinates
MAY 2003 ZHANG AND ROTHROCK 845 Modeling Global Sea Ice with a Thickness and Enthalpy Distribution Model in Generalized Curvilinear Coordinates JINLUN ZHANG AND D. A. ROTHROCK Polar Science Center, Applied Physics Laboratory, College of Ocean and Fishery Sciences, University of Washington, Seattle, Washington (Manuscript received 30 January 2002, in ®nal form 10 September 2002) ABSTRACT A parallel ocean and ice model (POIM) in generalized orthogonal curvilinear coordinates has been developed for global climate studies. The POIM couples the Parallel Ocean Program (POP) with a 12-category thickness and enthalpy distribution (TED) sea ice model. Although the POIM aims at modeling the global ocean and sea ice system, the focus of this study is on the presentation, implementation, and evaluation of the TED sea ice model in a generalized coordinate system. The TED sea ice model is a dynamic thermodynamic model that also explicitly simulates sea ice ridging. Using a viscous plastic rheology, the TED model is formulated such that all the metric terms in generalized curvilinear coordinates are retained. Following the POP's structure for parallel computation, the TED model is designed to be run on a variety of computer architectures: parallel, serial, or vector. When run on a computer cluster with 10 parallel processors, the parallel performance of the POIM is close to that of a corresponding POP ocean-only model. Model results show that the POIM captures the major features of sea ice motion, concentration, extent, and thickness in both polar oceans. The results are in reasonably good agreement with buoy observations of ice motion, satellite observations of ice extent, and submarine observations of ice thickness. -
Australian Hot and Dry Extremes Induced by Weakenings of the Stratospheric Polar Vortex
ARTICLES https://doi.org/10.1038/s41561-019-0456-x Australian hot and dry extremes induced by weakenings of the stratospheric polar vortex Eun-Pa Lim 1*, Harry H. Hendon 1, Ghyslaine Boschat 2,3, Debra Hudson 1, David W. J. Thompson4, Andrew J. Dowdy1 and Julie M. Arblaster 2,3,5 The occurrence of extreme hot and dry conditions in warm seasons can have large impacts on human health, energy and water supplies, agriculture and wildfires. Australian hot and dry extremes have been known to be associated with the occurrence of El Niño and other variations of tropospheric circulation. Here we identify an additional driver: variability of the stratospheric Antarctic polar vortex. On the basis of statistical analyses using observational data covering the past 40 yr, we show that weakenings and warmings of the stratospheric polar vortex, which episodically occur during austral spring, substantially increase the chances of hot and dry extremes and of associated fire-conducive weather across subtropical eastern Australia from austral spring to early summer. The promotion of these Australian climate extremes results from the downward coupling of the weakened polar vortex to tropospheric levels, where it is linked to the low-index polarity of the Southern Annular Mode, an equatorward shift of the mid-latitude westerly jet stream and subsidence and warming in the subtropics. Because of the long timescale of the polar vortex variations, the enhanced likelihood of early-summertime hot and dry extremes and wildfire risks across eastern Australia may be predictable a season in advance during years of vortex weakenings. nderstanding, predicting and anticipating extreme high the westerly vortex. -
Unprecedented Decline of Arctic Sea Ice out Ow in 2018
Unprecedented decline of Arctic sea ice outow in 2018 Hiroshi Sumata ( [email protected] ) Norwegian Polar Institute https://orcid.org/0000-0002-2832-2875 Laura de Steur Norwegian Polar Institute Sebastian Gerland Norwegian Polar Institute Dmitry Divine Norwegian Polar Institute Olga Pavlova Norwegian Polar Institute Article Keywords: Sea Ice Export, Climate and Deep Water Formation, Anomalous Atmospheric Circulation, Freshwater Cycle, Ice Thinning Posted Date: May 12th, 2021 DOI: https://doi.org/10.21203/rs.3.rs-376386/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License 1 Unprecedented decline of Arctic sea ice outflow in 2018 2 3 4 5 Hiroshi Sumata1*, Laura de Steur1, Sebastian Gerland1, Dmitry Divine1, Olga Pavlova1 6 1Norwegian Polar Institute, Fram Centre, Tromsø, Norway 7 8 9 * Correspondence to: Hiroshi Sumata ([email protected]) 10 11 12 13 14 15 16 17 Abstract 18 19 Fram Strait is the major gateway connecting the Arctic Ocean and North Atlantic Ocean, where nearly 90% 20 of the sea ice export from the Arctic Ocean takes place. The exported sea ice is a large source of freshwater 21 to the Nordic Seas and Subpolar North Atlantic, thereby preconditioning European climate and deep water 22 formation in the downstream North Atlantic Ocean. Here we show that in 2018, the ice export through Fram 23 Strait showed an unprecedented decline since the early 1990s. The 2018 ice export was reduced to less than 24 40% relative to that between 2000 and 2017, and amounted to just 25% of the 1990s. -
Physical Oceanography in the Arctic Ocean: 1968
Physical Oceanography in the Arctic Ocean: 1968 L. K. COACHMAN1 INTRODUCTION Three years ago I reviewed our knowledge of the physical regime of the Arctic Ocean (Coachman 1968). Briefly, the Ocean may be thought of as composed of two layers of different density: a light, relatively thin (W 200 m.) and well-mixed top layer overlying a large thick mass of water of extremely uniform salinity, and hence density. In cold seawater, the density is largely determined by the salinity. Superimposed on this regime is a three-layer temperature regime. The surface layer is cold, being at or near freezing. Frequently there is a tem- perature minimum near the bottom of the surface layer (- 150 to 200 m. depth), and within the Canada Basin a slight temperature maximum is found at 75 to 100 m. depth owing to the intrusion of Bering Sea water. The intermediate layer, Atlantic water, is above OOC., and below this layer (> 1000 m.) occurs the large mass of bottom water which has extremely uniform temperatures below 0°C. but definitely above freezing. The general picture of the water masses is drawn from 70 years of oceano- graphic data collection, The Naval Arctic Research Laboratory, in its support of drifting stations and other scientific work on the pack ice, has provided the basic support for the United States contribution to physical oceanographic studies of the central Arctic Ocean. There are still enormous gaps in our knowledge. The Arctic Ocean is probably no less complex than any of the world oceans, but its ranges of property values are less and hence the complexities are reflected as smallervariations of the values in space and time. -
Precursors of September Arctic Sea-Ice Extent Based on Causal Effect Networks
atmosphere Article Precursors of September Arctic Sea-Ice Extent Based on Causal Effect Networks Sha Li 1, Muyin Wang 2,3,*, Nicholas A. Bond 2,3, Wenyu Huang 1 , Yong Wang 1, Shiming Xu 1 , Jiping Liu 4, Bin Wang 1,5 and Yuqi Bai 1,* 1 Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing 100084, China; [email protected] (S.L.); [email protected] (W.H.); [email protected] (Y.W.); [email protected] (S.X.); [email protected] (B.W.) 2 Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA 98195, USA; [email protected] 3 Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, WA 98115, USA 4 Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York, Albany, NY 12222, USA; [email protected] 5 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China * Correspondence: [email protected] (M.W.); [email protected] (Y.B.); Tel.: +1-206-526-4532 (M.W.); +86-10-6279-5269 (Y.B.) Received: 1 October 2018; Accepted: 2 November 2018; Published: 9 November 2018 Abstract: Although standard statistical methods and climate models can simulate and predict sea-ice changes well, it is still very hard to distinguish some direct and robust factors associated with sea-ice changes from its internal variability and other noises. -
The Response of the Antarctic Oscillation to Increasing and Stabilized
15 MAY 2003 CAI ET AL. 1525 The Response of the Antarctic Oscillation to Increasing and Stabilized Atmospheric CO2 WENJU CAI AND PETER.H.WHETTON CSIRO Atmospheric Research, Aspendale, Victoria, Australia DAVID J. KAROLY School of Mathematical Sciences, Monash University, Victoria, Australia (Manuscript received 6 June 2002, in ®nal form 14 October 2002) ABSTRACT Recent results from greenhouse warming experiments, most of which follow the Intergovernmental Panel on Climate Change (IPCC) IS92a scenario, have shown that under increasing atmospheric CO 2 concentration, the Antarctic Oscillation (AAO) exhibits a positive trend. However, its response during the subsequent CO 2 stabi- lization period has not been explored. In this study, it is shown that the upward trend of the AAO reverses during such a stabilization period. This evolution of an upward trend and a subsequent reversal is present in each ensemble of three greenhouse simulations using three versions of the CSIRO Mark 2 coupled climate model. The evolution is shown to be linked with that of surface temperature, which also displays a corresponding trend and reversal, incorporating the well-known feature of interhemispheric warming asymmetry with smaller warming in the Southern Hemisphere (smaller as latitude increases) than that in the Northern Hemisphere during the transient period, and vice versa during the stabilization period. These results indicate that once CO 2 con- centration stabilizes, reversal of the AAO trend established during the transient period is likely to be a robust feature, as it is underpinned by the likelihood that latitudinal warming differences will reduce or disappear. The implication is that climatic impacts associated with the AAO trend during the transient period may be reversible if CO2 stabilization is achieved. -
Arctic Oscillation and Antarctic Oscillation in Internal Atmospheric Variability with an Ensemble AGCM Simulation
ADVANCES IN ATMOSPHERIC SCIENCES, VOL. 24, NO. 1, 2007, 152–162 Arctic Oscillation and Antarctic Oscillation in Internal Atmospheric Variability with an Ensemble AGCM Simulation ∗1 1,2 3 Ó Ä LU Riyu (ö ), LI Ying ( ), and Buwen DONG 1State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) and Center for Monsoon System Research (CMSR), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 2Graduate University of the Chinese Academy of Sciences, Beijing 100039 3National Centre for Atmospheric Science-Climate (NCAS) Centre for Global Atmospheric Modelling, Department of Meteorology, University of Reading, Reading, United Kingdom (Received 5 January 2006; revised 3 July 2006) ABSTRACT In this study, we investigated the features of Arctic Oscillation (AO) and Antarctic Oscillation (AAO), that is, the annular modes in the extratropics, in the internal atmospheric variability attained through an en- semble of integrations by an atmospheric general circulation model (AGCM) forced with the global observed SSTs. We focused on the interannual variability of AO/AAO, which is dominated by internal atmospheric variability. In comparison with previous observed results, the AO/AAO in internal atmospheric variability bear some similar characteristics, but exhibit a much clearer spatial structure: significant correlation be- tween the North Pacific and North Atlantic centers of action, much stronger and more significant associated precipitation anomalies, and the meridional displacement of upper-tropospheric westerly jet streams in the Northern/Southern Hemisphere. In addition, we examined the relationship between the North Atlantic Oscillation (NAO)/AO and East Asian winter monsoon (EAWM). It has been shown that in the internal atmospheric variability, the EAWM variation is significantly related to the NAO through upper-tropospheric atmospheric teleconnection patterns. -
Teleconnections and Relationship Between ENSO and SAM in Reconstructions and Models Over the Past Millennium Christoph Dätwyler1, Martin Grosjean1, Nathan J
https://doi.org/10.5194/cp-2019-110 Preprint. Discussion started: 9 September 2019 c Author(s) 2019. CC BY 4.0 License. Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium Christoph Dätwyler1, Martin Grosjean1, Nathan J. Steiger2, Raphael Neukom1 1Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland 5 2Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA Correspondence to: Christoph Dätwyler ([email protected]) Abstract. The climate of the Southern Hemisphere (SH) is strongly influenced by variations in the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Due to the temporally very limited instrumental records in most parts of the SH, very little is known about the relationship between these two key modes of variability and its stability over 10 time. Here, we use proxy-based reconstructions and climate model simulations to quantify changes in tropical-extratropical SH teleconnections as represented by the correlation between the ENSO and SAM indices. Reconstructions indicate mostly negative correlations back to around 1400 CE confirming the pattern seen in the instrumental record over the last few decades. An ensemble of last millennium simulations of the model CESM1 confirms this pattern with very stable ensemble mean correlations around -0.3. Individual forced simulations, the pre-industrial control run and the proxy-based reconstructions 15 indicate intermittent periods of positive correlations and particularly strong negative correlations. The fluctuations of the ENSO-SAM correlations are not significantly related to solar nor volcanic forcing in both proxy and model data, indicating that they are driven by internal variability in the climate system. -
The Southern Annular Mode: a Comparison of Indices M
Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Hydrol. Earth Syst. Sci. Discuss., 8, 7461–7498, 2011 Hydrology and www.hydrol-earth-syst-sci-discuss.net/8/7461/2011/ Earth System doi:10.5194/hessd-8-7461-2011 Sciences © Author(s) 2011. CC Attribution 3.0 License. Discussions This discussion paper is/has been under review for the journal Hydrology and Earth System Sciences (HESS). Please refer to the corresponding final paper in HESS if available. The Southern Annular Mode: a comparison of indices M. Ho, A. S. Kiem, and D. C. Verdon-Kidd Environmental and Climate Change Research Group, School of Environmental and Life Sciences, Faculty of Science and Information Technology, University of Newcastle, Australia Received: 15 June 2011 – Accepted: 15 July 2011 – Published: 1 August 2011 Correspondence to: M. Ho ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. 7461 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract The Southern Annular Mode (SAM) has been identified as a climate mechanism with potentially significant impacts on the Australian hydroclimate. However, despite the identification of some relationships between SAM and Australia’s hydroclimate, the as- 5 sociation has not been extensively explored or robustly quantified. Further complicating the situation is the existence of numerous indices (or methods) by which SAM has been approximated. In this paper, the various SAM definitions and indices are reviewed and the similarities and discrepancies are discussed, along with the strengths and weak- nesses of each index development approach. Further, the sensitivity of the relationship 10 between SAM and Australian rainfall on choice of SAM index is quantified and recom- mendations are given as to the most appropriate index to use when assessing the impacts of the SAM on Australia’s hydroclimate. -
Record Winter Winds in 2020/21 Drove Exceptional Arctic Sea Ice Transport ✉ R
ARTICLE https://doi.org/10.1038/s43247-021-00221-8 OPEN Record winter winds in 2020/21 drove exceptional Arctic sea ice transport ✉ R. D. C. Mallett 1 , J. C. Stroeve1,2,3, S. B. Cornish 4, A. D. Crawford 3, J. V. Lukovich3, M. C. Serreze2, A. P. Barrett2, W. N. Meier2, H. D. B. S. Heorton 1 & M. Tsamados1 The volume of Arctic sea ice is in decline but exhibits high interannual variability, which is driven primarily by atmospheric circulation. Through analysis of satellite-derived ice products and atmospheric reanalysis data, we show that winter 2020/21 was characterised by anomalously high sea-level pressure over the central Arctic Ocean, which resulted in unprecedented anticyclonic winds over the sea ice. This atmospheric circulation pattern 1234567890():,; drove older sea ice from the central Arctic Ocean into the lower-latitude Beaufort Sea, where it is more vulnerable to melting in the coming warm season. We suggest that this unusual atmospheric circulation may potentially lead to unusually high summer losses of the Arctic’s remaining store of old ice. 1 Centre for Polar Observation and Modelling, Earth Sciences, University College London, London, UK. 2 National Snow and Ice Data Center, CIRES, University of Colorado, Boulder, CO, USA. 3 Centre for Earth Observation Science, University of Manitoba, Winnipeg, Canada. 4 Department of Earth Sciences, ✉ University of Oxford, Oxford, UK. email: [email protected] COMMUNICATIONS EARTH & ENVIRONMENT | (2021) 2:149 | https://doi.org/10.1038/s43247-021-00221-8 | www.nature.com/commsenv 1 ARTICLE COMMUNICATIONS EARTH & ENVIRONMENT | https://doi.org/10.1038/s43247-021-00221-8 heage,extent,thicknessandvolumeofArcticseaicearein A measure of anticyclonic flow is the relative vorticity7.Relative multidecadal decline1,2.However,thesequantitiesallexhibit vorticity of the 10-m winds over Arctic Ocean sea ice fell more than T – − year-to-year variability, which is in part determined by vari- 2.3 standard deviations below 1979 2021 mean (Fig. -
El Niño Southern Oscillation Signal in a New East Antarctic Ice Core, Mount Brown South
https://doi.org/10.5194/cp-2020-134 Preprint. Discussion started: 10 November 2020 c Author(s) 2020. CC BY 4.0 License. El Niño Southern Oscillation signal in a new East Antarctic ice core, Mount Brown South 1 1 1 2 3 Camilla K. Crockart , Tessa R. Vance , Alexander D. Fraser , Nerilie J. Abram , Alison S. Criscitiello , Mark A.J. Curran4,1, Vincent Favier5, Ailie J.E. Gallant6, Helle A. KJær7, Andrew R. Klekociuk4,1, 5 Lenneke M. Jong4,1, Andrew D. Moy4,1, Christopher T. Plummer1, Paul T. Vallelonga7,#, Jonathon Wille5, and Lingwei Zhang8 1Australian Antarctic Program Partnership, Institute for Marine & Antarctic Studies, University of Tasmania, Hobart 7004, Australia. 2Research School of Earth Sciences and ARC Centre of Excellence for Climate Extremes, Australian National University, 10 Canberra ACT 2601, Australia. 3Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, T6G 2R3, Canada. 4Australian Antarctic Division, Channel Highway, Kingston 7050, Australia. 5Institut des Géosciences de l’Environnement, Université Grenoble-Alpes, Grenoble, France. 6School of Earth, Atmosphere and Environment, Monash University, Rainforest Walk, Clayton 3800, Victoria. 15 7Physics of Ice, Climate and Earth, Niels Bohr Institute, University of Copenhagen, Denmark. 8Institute for Marine & Antarctic Studies, University of Tasmania, Hobart 7004, Australia. Correspondence to: Camilla K. Crockart ([email protected]) #Now at UWA Oceans Institute, University of Western Australia, Perth 6909, Australia. 20 Abstract Paleoclimate archives, such as high-resolution ice core records, provide a means to investigate long-term (multi-centennial) climate variability. Until recently, the Law Dome (Dome Summit South) ice core record remained one of few long-term high- resolution records in East Antarctica. -
New Definition Antarctic Oscillation Index
1 Definition of Antarctic Oscillation Index Daoyi Gong and Shaowu Wang Department of Geophysics, Peking University, P.R. China Abstract. Following Walker’s work about his famous three oscillations published during the 1920-30s, many papers were written about atmospheric oscillations. A fourth atmospheric oscillation in the middle and high southern latitudes was found, and named the Antarctic Oscillation (AO). AO refers to a large scale alternation of atmospheric mass between the mid-latitudes and high latitudes surface pressure. In order to understand the spatial structure of sea level pressure variation in detail, empirical orthogonal function analysis is applied. An objective index of the Antarctic Oscillation Index (AOI) is defined as the difference of zonal mean sea level pressure between 40°S and 65°S. The AOI has the potential for clarifying climate regimes in the southern hemisphere, similar to how the NAO and the NPO has been used in the northern hemisphere. Introduction During the past one hundred years, much attention has been given to low-level atmospheric circulation for understanding the local to planetary scale climatic anomalies. During the 1920-1930s, a comprehensive study on atmospheric oscillations was carried out by Sir Gilbert Walker. Three oscillations were revealed and named as “North Atlantic Oscillation (NAO)”, “North Pacific Oscillation (NPO)” and “Southern Oscillation (SO)”. Numerical definitions of the three oscillations were also given by Walker [Montgomery, 1940]. A large number of papers about these oscillations were published after Walker, and more details were also revealed. Were there other oscillation(s) besides NAO, NPO and SO, especially in the southern hemisphere? It had been supposed that there might be other atmospheric oscillation(s) in the high southern latitudes.