Antarctic Climate Change and the Environment

Antarctic Climate Change and the Environment This volume provides a comprehensive, up-to-date account of how the physical and biological environment of the Antarctic continent and Southern Ocean has changed from Deep Time until the present day. It also considers how the Antarctic environment may change over the next century in a world where greenhouse gas concentrations are much higher than occurred over the last few centuries. The Antarctic is a highly coupled system with non-linear interactions between the atmosphere, ocean, ice and biota, along with complex links to the rest of the Earth system. In preparing this volume our approach has been highly cross-disciplinary, with the goal of reflecting the importance of the continent in global issues, such as sea level rise, the separation of natural climate variability from anthropogenic influences, food stocks, biodiversity and carbon uptake by the ocean. One hundred experts in Antarctic science have contributed and drafts of the manuscript were reviewed by over 200 scientists. We hope that it will be of value to all scientists with an interest in the Antarctic continent and the Southern Ocean, policy makers and those concerned with the deployment of observing systems and the development of climate models. JOHN TURNER is a research scientist at the British Antarctic Survey in Cambridge, UK where he leads a project investigating recent Antarctic climate change and how it may change over the next century. He has had a long involvement with SCAR and was the Chief Officer of the Physical Sciences Standing Scientific Group from 2002 to 2006 and chaired the steering committee of the SCAR programme on Antarctica and the Global Climate System from 2005 to 2008. He is the co-author of ‘Antarctic Meteorology and Climatology’ and ‘Polar Lows: Mesoscale Weather Systems in the Polar Regions’, both of which were published by Cambridge University Press. He was awarded the International Journal of Climatology Prize of the Royal Meteorological Society in 2005. ROBERT BINDSCHADLER is Chief Scientist of NASA's Hydrospheric and Biospheric Sciences Laboratory, a Senior Fellow of the Goddard Space Flight Center, a Fellow of the American Geophysical Union and a past President of the International Glaciological Society. He maintains an active interest in glaciers and ice sheets and has led 15 Antarctic field expeditions to study dynamics of the West Antarctic ice sheet. During his 29 years at NASA, he has developed numerous unique applications of remote sensing data for glaciological research including measuring ice velocity and elevation using both visible and radar imagery, monitoring melt of the ice sheet by microwave emissions, and detecting changes in ice-sheet volume by repeat space- borne radar altimetry. He has testified before Congress, briefed the U.S. Vice President, published over 140 scientific papers, including numerous review articles and is often quoted commenting on glaciological impacts of the climate on the world's ice sheets and glaciers. PETER CONVEY is a research scientist at the British Antarctic Survey in Cambridge, UK where he is the senior terrestrial ecologist in a wide-ranging programme investigating ecosystem structure and function in the Antarctic, and how this responds to environmental variability and change. He has wide research interests ranging from genomics and ecophysiology to historical biogeography. He is Co-Chair of the current SCAR Science Research Programme 'Evolution and Biodiversity in Antarctica' (2005-2013), and was a Steering Committee member of its predecessor programme 'Regional Sensitivity to Climate Change in Antarctica' (2000-2005). He is a co-editor of ‘Trends in Antarctic Terrestrial and Limnetic Ecosystems: Antarctica as a Global Indicator’, published by Springer. GUIDO DI PRISCO is a Director of Research of the Italian National Research Council (CNR). His expertise lies in Biochemistry and Molecular Biology, and his particular interests in molecular adaptation and evolution in polar oceans and the impact of climate change. He has undertaken 13 expeditions at Mario Zucchelli Station in the Ross Sea, and 6 at Palmer Station on the Antarctic Peninsula, and participated in 3 research cruises in the Antarctic/sub-Antarctic. A member of SCAR's Standing Scientific Group on Life Sciences, he is Co-Chair of SCAR's research programme on Evolution and Biodiversity in the Antarctic, and helped to steer its predecessor biological programmes. Guido has been Guest Editor of 5 books in his subject area, and of a number of Special Issues of high impact journals in his field. He is author or co-author of over 280 peer-reviewed articles. EBERHARD FAHRBACH is a research scientist at the Alfred-Wegener-Institut für Polar-und Meeresforschung and head of the Observational Oceanography section. He has the position of scientific coordinator of RV “Polarstern”. He is working on water masses and circulation in Polar oceans. He has participated in 18 cruises to the Antarctic and the Arctic most of them as chief scientist. He was and is a member of a variety of national and international steering groups and committees. In 2007 he was awarded the Georg Wüst Prize by the Deutsche Gesellschaft für Meeresforschung. JULIAN GUTT is a research scientist at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, and has been involved in polar research for 25 years. His interests focus on ecosystem responses to climate-induced disturbance. In 2006/07 he was the principal investigator of an expedition to the area where the Larsen A and B ice shelves had recently disintegrated, to examine the way in which these areas were being recolonised by new organisms. He is a member of the steering committee of the "Census of Antarctic Marine Life". Together with John Turner, he chairs SCAR's Action Group on "Prediction of Changes in the Physical and Biological Environments of the Antarctic". Besides many scientific articles he has written several chapters for popular books on marine biodiversity and environmental change. DOMINIC HODGSON is a research scientist at the British Antarctic Survey in Cambridge, UK. He is a Quaternary Scientist with a particular interest in high latitude environmental change. His current research involves using lake sediments, as well as polar marine sediment and ice cores, to investigate how different parts of the Earth System have interacted to produce the large climate changes that occurred naturally in the past. Recent career highlights include developing new relative sea level curves for Antarctica, reconstructing the Holocene history of Antarctic Peninsula ice shelves, documenting climate history from lakes that have survived through glacial cycles, and working on a recently emerged subglacial lake. Dr Hodgson has led research in many regions of Antarctica including east Antarctica, the Antarctic Peninsula, Maritime Antarctic and Subantarctic Islands. PAUL ANDREW MAYEWSKI is Director and Professor of the Climate Change Institute at the University of Maine. He has led more than 50 research expeditions throughout polar and high mountain regions including leadership of the 25 institution Greenland Ice Sheet Project Two and the 21 nation International Trans Antarctic Scientific Expedition. He has authored more than 300 peer reviewed articles and appears regularly in public media venues discussing climate change. In 2006 he was awarded the SCAR Medal for Excellence in Antarctic Research. COLIN SUMMERHAYES is a geologist with an extensive career in oceanography, whose most recent scientific research has been on how climate change affected ocean currents and oceanic productivity during the past 100,000 years. A former Director of the UK's Institute of Oceanographic Sciences Deacon Laboratory, now part of the National Oceanography Centre, Southampton, UK, he spent 7 years as Director of the Global Ocean Observing System Project for UNESCO's Intergovernmental Oceanographic Commission in Paris before joining SCAR as Executive Director in 2004. He is a co-author of ‘Oceans 2020, Science, Trends and the Challenge of Sustainability, published by Island Press; of ‘Oceanography: an Illustrated Guide, published by Manson Publishing; and of ‘Upwelling in the Oceans’ published by Wiley. Antarctic Climate Change and the Environment Editors: John Turner Robert Bindschadler Pete Convey Guido di Prisco Eberhard Fahrbach Julian Gutt Dominic Hodgson Paul Mayewski Colin Summerhayes Published by the Scientific Committee on Antarctic Research Scott Polar Research Institute, Lensfield Road, Cambridge, UK Version 1.1 25 November 2009 © Scientific Committee on Antarctic Research, 2009. ISBN 978-0-948277-22-1 Printed by Victoire Press, 1 Trafalgar Way, Bar Hill, Cambridge CB23 8SQ. Cover © British Antarctic Survey; designed by Jamie Oliver. CONTENTS PREFACE ……………………………………………………………………………………… ix EXECUTIVE SUMMARY …………………………………………………………………….. x 1 THE ANTARCTIC ENVIRONMENT AND THE GLOBAL SYSTEM ………………. 1 1.1 THE PHYSICAL SETTING ……………………………………………………………………. 1 1.2 THE ANTARCTIC CRYOSPHERE …………………………………………………………… 4 1.3 THE ROLE OF THE ANTARCTIC IN THE GLOBAL CLIMATE SYSTEM ……………… 10 1.4 OBSERVATIONS FOR STUDIES OF ENVIRONMENTAL CHANGE IN THE ANTARCTIC ………………………………………………………………………………….. 17 1.5 THE CLIMATE OF THE ANTARCTIC AND ITS VARIABILITY ………………………… 18 1.6 BIOTA OF THE ANTARCTIC ……………………………………………………………….. 21 1.6.1 Terrestrial ……………………………………………………………………………….. 23 1.6.2 Marine …………………………………………………………………………………... 26 2 OBSERVATIONS, DATA ACCURACY AND TOOLS ……………………………….. 33 2.1 OBSERVATIONS, DATA ACCURACY AND TOOLS ……………………………………... 33 2.1.1 Introduction …………………………………………………………………………….. 33 2.1.2 Meteorological and ozone observing in the Antarctic ………………………………….. 34 2.1.3 In-situ ocean observations ………………………………………………………………. 47 2.1.4 Sea ice observations …………………………………………………………………….. 60 2.1.5 Observations of the ice sheet and permafrost ……………………………………………64 2.1.6 Sea level ………………………………………………………………………………… 79 2.1.7 Marine biology ………………………………………………………………………….. 82 2.1.8 Terrestrial biology ………………………………………………………………………. 85 2.1.9 Models ………………………………………………………………………………….. 88 2.2 FUTURE DEVELOPMENTS AND RESEARCH NEEDS …………………………………. 113 3 ANTARCTIC CLIMATE AND ENVIRONMENT HISTORY IN THE PRE- INSTRUMENTAL PERIOD …………………………………………………………… 115 3.1 INTRODUCTION ……………………………………………………………………………. 115 3.2 DEEP TIME ………………………………………………………………………………….. 118 3.2.1 The Greenhouse world: from Gondwana breakup to 34 million years…...……………..... 119 3.2.2 Into the Icehouse world: the last 34 million years ….…….…………………………..….. 122 3.3 THE LAST MILLION YEARS………………………………………………………………. 126 3.3.1 Glacial interglacial cycles: the ice core record………………..................................…….. 126 3.3.2 The transition to Holocene interglacial conditions: the ice core record……………….…. 133 3.3.3 Deglaciation of the continental shelf, coastal margin and continental interior………..….. 138 3.3.4 Antarctic deglaciation and its impact on global sea level………………………..……….. 140 3.3.5 Sea ice and climate ……………………..……………………………………………….... 144 3.4 THE HOLOCENE ……………………………………………………………………………. 147 3.4.1 Holocene climate change: regional to hemispheric perspectives .............................…….. 147 3.4.2 Changes in sea ice extent through the Holocene………….......................................…….. 155 3.4.3 Regional patterns of Holocene climate change in Antarctica....................................…….. 159 3.5 BIOLOGICAL RESPONSES TO CLIMATE CHANGE ……………………………………. 170 3.5.1 The terrestrial environment ……………………………………...............................…….. 170 3.5.2 The marine environment…………............................................................................…….. 173 v 3.4.3 Regional patterns of Holocene climate change in Antarctica....................................…….. 159 3.6 CONCLUDING REMARKS ……………………………………………………………..….. 180 4 THE INSTRUMENTAL PERIOD ……………………………………………………... 183 4.1 INTRODUCTION ……………………………………………………………………………. 183 4.2 CHANGES OF ATMOSPHERIC CIRCULATION………………………………………….. 184 4.2.1 Modes of variability .............................……………………………………………….….. 184 4.2.2 Depression tracks .............................………………………………………………….….. 191 4.2.3 Teleconnections .............................…………………………...……………………….…..193 4.3 TEMPERATURE ……………………………………………………………………………. 195 4.3.1 Surface temperature .............................……………………………………………….….. 195 4.3.2 Upper air temperature changes.............……………………………………………….….. 202 4.3.3 Attribution .............................………………………...……………………………….….. 204 4.4 CHANGES IN ANTARCTIC SNOWFALL OVER THE PAST 50 YEARS………………... 204 4.4.1 General spatial and temporal characteristics of Antarctic snowfall.…………………….... 204 4.4.2 Long-term Antarctic snowfall accumulation estimates.……………………..………….... 205 4.4.3 Recent trends in Antarctic snowfall.…………………………………………………….... 206 4.5 ATMOSPHERIC CHEMISTRY…………………………………………………………...…. 208 4.5.1 Antarctic stratospheric ozone in the instrumental period.…………………………...….... 208 4.5.2 Antarctic tropospheric chemistry.…………………………………………….……...….... 211 4.5.3 Aerosol, clouds and radiation.………………………………………………...……...….... 216 4.6 THE SOUTHERN OCEAN………………………………………………….……………….. 220 4.6.1 Introduction.………………………………………………………………………….….... 220 4.6.2 Australian sector.…………………………………………………………………….….... 222 4.6.3 The Amundsen/Bellingshausen Seas………………………………………………...….... 225 4.6.4 Variability and change in Ross Sea shelf waters…………………………………….….... 226 4.6.5 The Weddell Sea sector……………………………………………………………...….... 229 4.6.6 Small-scale processes in the Southern Ocean…………….…............................................. 232 4.6.7 Dynamics of the circulation and water masses of the ACC and the polar gyres from model results.………………………………………………………………….…….….... 235 4.7 ANTARCTIC SEA ICE COVER DURING THE INSTRUMENTAL PERIOD ……………. 236 4.7.1 Introduction.………………………………………………………………………….….... 236 4.7.2 Sea ice cover in the pre-satellite era…………………………………………………….... 236 4.7.3 Variability and trends in sea ice using satellite data……………………………...….….... 238 4.8 THE ICE SHEET AND PERMAFROST ……………………………………………………. 243 4.8.1 Introduction.………………………………………………………………………….….... 243 4.8.2 The Antarctic Peninsula………………………………………………………..…….….... 245 4.8.3 West Antarctica.………………………………………………………………….……….. 252 4.8.4 East Antarctica……………………………………………………………………….….... 256 4.8.5 Calving.…………………………………………………………...………………….….... 257 4.8.6 Sub-glacial water movement……………………………………...………………….….... 257 4.8.7 Other changes in the ice sheet.……………………………………………………….….... 257 4.8.8 Attribution of changes to the ice sheet….………………………...………………….….... 257 4.8.9 Conclusions regarding the ice sheet………………………...…………………….….….... 260 4.8.10 Changes in Antarctic permafrost and active layer over the last 50 years.......................... 261 4.9 LONG TERM SEA LEVEL CHANGE ……………………………………………………. 262 4.10 MARINE BIOLOGY …………………………………………………...……………………. 263 4.10.1 The open ocean system……………………………………………….…………….….... 263 4.10.2 Sea ice ecosystems……………………………………………….…………………….... 270 4.10.3 ENSO links and teleconnections to vertebrate life histories and population…….…….... 270 4.10.4 Invertebrate physiology……………………………………………….…………….….... 272 4.10.5 Seasonality effect on the high Antarctic benthic shelf communities?…………………... 276 vi 4.10.6 Macroalgal physiology and ecology……………………………………………...……... 278 4.10.7 Marine/terrestrial pollution…………………………………………………………….... 280 4.11 BIOGEOCHEMISTRY – SOUTHERN OCEAN CARBON CYCLE RESPONSE TO HISTORICAL CLIMATE CHANGE ……………………………..…………………………. 286 4.11.1 Introduction……………………………………………….……………..………….….... 286 4.11.2 CO fluxes in the Southern Ocean…….……………..………….……………………..... 286 2 4.11.3 Historical change – observed response ……………………...….……………………..... 288 4.11.4 Historical change – simulated view……….……………………………………….…..... 290 4.11.5 Changes in CO inventories……….……………………………………………….…..... 291 2 4.11.6 Concluding remarks……….……………………………………………………….…..... 293 4.12 TERRESTRIAL BIOLOGY …………………………………………………………………. 293 5 THE NEXT 100 YEARS ………………………………………………………………... 299 5.1 INTRODUCTION ……………………………………………………………………………. 299 5.2 CLIMATE CHANGE…………………………………………………………………………. 300 5.2.1 IPCC scenarios .............................…………………………………………………….….. 300 5.2.2 Climate models .............................…………………………………………………....….. 303 5.2.3 Atmospheric circulation..................………………………………………………..….….. 307 5.2.4 Temperature change over the Twenty First Century………………….………………….. 312 5.2.5 Precipitation change over the Twenty First Century .........…………….……………….... 316 5.2.6 Antarctic stratospheric ozone over the next 100 years .........…………….………………. 319 5.3 OCEAN CIRCULATION AND WATER MASSES…………………………………..…….. 326 5.3.1 Simulation of present-day conditions in the Southern Hemisphere ....…………………… 326 5.3.2 Projections for the Twenty First Century ....……………………………………………… 327 5.3.3 Long-term evolution of the Southern Ocean ....……………………………………......… 335 5.3.4 Conclusions ....………………………………………………………………………….… 336 5.4 SEA ICE CHANGE OVER THE TWENTY FIRST CENTURY…………………………..... 337 5.5 THE TERRESTRIAL CRYOSPHERE……………………………………………………….. 339 5.5.1 Introduction……………………………………………….……………..………….….... 339 5.5.2 East Antarctic ice sheet…………………….……………..………………………….….... 340 5.5.3 West Antarctic ice sheet…………….……………..………………………………...….... 341 5.5.4 Antarctic Peninsula……………….……………..…………………………………...….... 343 5.5.5 Conclusions……………………………………………….……………..…..……….….... 343 5.5.6 Summary and needs for future research….……………..………….…............................... 344 5.6 EVOLUTION OF ANTARCTIC PERMAFROST……………………………………….….. 345 5.7 PROJECTIONS OF SEA LEVEL IN ANTARCTIC AND SOUTHERN OCEAN WATERS BY 2100 …………………………………………………………………………... 345 5.7.1 Regional projections of mean sea-level rise….……………..………….……………….... 347 5.8 BIOGEOCHEMISTRY – RESPONSE OF THE SOUTHERN OCEAN CARBON CYCLE TO FUTURE CLIMATE CHANGE……………………………………………….... 349 5.8.1 Background….……………..………….………………………………………………...... 349 5.8.2 Future Southern Ocean carbon response….……………..…………………………...….... 349 5.8.3 Response to increased CO uptake….……………..………………………………...….... 352 2 5.8.4 Concluding remarks….……………..………….………………………………………..... 354 5.9 BIOLOGY…………………………………………………………………………………….. 354 5.9.1 Terrestrial Biology….……………..………………………………………………....….... 355 5.9.2 Marine Biology….……………..…………………………………………………….….... 357 5.9.3 The Antarctic marine ecosystem in the year 2100….……………..………….………....... 383 6 RECOMMENDATIONS ………………………………………………………………...389 7 REFERENCES ………………………………………………………………………….. 395 vii viii Preface To understand how planet Earth works we study it increasingly as a system – a collection of interdependent parts or spheres – the lithosphere, the hydrosphere, the cryosphere, the biosphere and the atmosphere. Understanding how these spheres are connected and how they interact improves our ability to forecast how one or a combination of them may change in response to external forcings caused for example by the advent of volcanic eruptions, solar variability or human activities. One of the remotest parts of the Earth system is Antarctica, a continent larger than either Australia or Europe. We will not be able to fully understand how the Earth system works without comprehensive knowledge of the physical, biological, chemical and geological processes taking place within and above Antarctica and its surrounding Southern Ocean. That is a huge challenge given that these processes take place among some of the remotest and harshest environments anywhere on the Earth’s surface. Currents and waves in the global ocean and the atmosphere ensure that Antarctica is affected by what happens elsewhere on the planet. Equally, ocean and atmospheric processes ensure that what happens in Antarctica may affect the rest of the world. It is the world’s freezer. Much has been achieved in acquiring knowledge of Antarctica’s physical, biological, chemical and geological processes, especially since a network of permanent scientific stations was established for the first time on the continent during the International Geophysical Year of 1957-58. Many more results will emerge from the recently completed International Polar Year of 2007-2008. Nevertheless, the practicalities and expense involved in getting scientists to these remote and harsh places means that this region will remain under-sampled for years to come, constraining what can be achieved in the way of both understanding and forecasts. What we set out to do in this volume is to review present understanding of the physical and chemical climate system of the Antarctic region, the way it varies through time, and the profound influence of that variation on life on land and in the ocean around the continent. We then use this as the basis for predicting, albeit crudely within the limits of the dearth of information compared with the other continents, what may happen in the future as greenhouse gases build up in the atmosphere and as the ozone hole starts to diminish. This volume should be taken as a companion to the Arctic Climate Impact Assessment published in 2005. The work has been carried out under the editorial control of representatives of three of SCAR’s five major scientific research programmes: Antarctica in the Global Climate System (AGCS), Antarctic Climate Evolution (ACE), and Evolution and Biodiversity in the Antarctic (EBA). The process began in 2005 when the SCAR Executive Committee meeting in Sofia, Bulgaria (July 11-13, 2005) agreed that an Antarctic Climate Impact Assessment should be produced for the guidance of policy makers in the Antarctic Treaty System and to inform the public. The plan for the assessment was fleshed out at the first SCAR Cross-Linkages Workshop, in Amsterdam (November 15-17, 2005) (http://www.scar.org/researchgroups/crosslinkages/Amsterdam_Meeting_Report.pdf). Phase I focused on the physics of the climate system. The plans were presented to policy makers at the Antarctic Treaty Consultative Meeting in Edinburgh in 2006 (http://www.scar.org/treaty/atcmxxix/atcm29_ip089.pdf). Initial results were presented to policy makers at the Antarctic Treaty Consultative Meeting in New Delhi in 2007 (http://www.scar.org/treaty/atcmxxx/Atcm30_ip005_e.pdf) and published in the journal Reviews in Geophysics in January 2009 (Mayewski et al., 2009). In the meantime work had begun on Phase II, incorporating biology and chemistry, and preliminary results were presented to policy makers at the Antarctic Treaty Consultative Meeting in Kiev in 2008 (http://www.scar.org/treaty/atcmxxxi/ATCM31_IP62_ACCE.pdf), with final results being ix