Reconstructing wind strength and atmospheric circulation in West Antarctica over the past 300 years

Lead Research Organisation: NERC British Antarctic Survey
Department Name: Science Programmes

Abstract

Southern Ocean winds drive exchanges of heat and carbon dioxide between the ocean and the atmosphere, acting as a principal driver in regulating the global meridional overturning circulation. It is claimed that winds over the Southern Ocean (circumpolar westerlies) have increased in strength and shifted closer to the Antarctic continent in recent decades and is one of the strongest trends in Southern Hemisphere climate over the last 30 years. The enhanced circumpolar westerlies, attributed to greenhouse warming and anthropogenic ozone depletion, has driven changes in the depth of the ocean surface mixed layer and led to enhanced upwelling of deep, carbon-rich water. Regionally, changes in wind strength and atmospheric circulation patterns have been linked to the observed warming and increased precipitation on the Antarctica Peninsula and to increased upwelling of warm circumpolar deep water onto the Antarctic continental shelf. Circumpolar deep water promotes accelerated melting and thinning at the base of ice shelves and is considered a major contributing factor in the recent collapse of many Antarctic Peninsula ice shelves and a threat to the stability of large ice shelves in the Bellingshausen and Amundsen Sea.

Few instrumental records of Southern Ocean winds exist prior to the late 20th century making it hard to validate models which examine the roles of wind strength and circulation on upwelling and climate. Climate models predict a poleward shift and strengthening of surface winds in response to increased atmospheric CO2 and therefore it is imperative that we understand how Southern Ocean wind patterns have changed over longer timescales and their potential impact on regional and ultimately global climate.

In this proposal we will produce the first ice-core multi-proxy reconstruction of past wind strength and atmospheric circulation in the Bellingshausen and Amundsen Seas. The innovative proxy records will be developed using two new ice cores drilled on the climatically sensitive Amundsen Sea coast, West Antarctica which cover the period 2010-1700 AD. The unique discovery of marine diatoms in these ice cores, uplifted from the surface of the Amundsen/ Bellingshausen Sea and transported to the ice core sites by onshore (northerly) winds, will be used to provide a record of local changes in wind strength. This will be combined with records of dust and continental ions measured in the ice cores, which are proven proxies for long-range (circumpolar westerly) wind strength and circulation. Additional isotopic measurements will be taken to assess changes in the moisture source regions and the location of the Southern Hemisphere wind belt and a proven ice core proxy for past sea ice extent (Methansulphonic acid) will be measured to determine how sea ice influences uplift and transport of the diatoms deposited in the ice core.

This interdisciplinary study will be the first of its kind to incorporate marine, continental and atmospheric tracers, to reconstruct both regional and hemispheric wind strength and atmospheric circulation in the Amundsen/Bellingshausen Sea. We will have an enhanced set of proxies to establish the drivers governing climate variability and an opportunity to explore the true impact of Southern Ocean winds on regional climate and upwelling in West Antarctica and the Amundsen/ Bellingshausen Sea. The new reconstructions will provide a much needed record of decadal to centennial changes and a means to test the intrinsic variability of climate models currently used to predict future climate change in this region.

Planned Impact

The research undertaken in this project will improve our understanding of how winds and atmospheric circulation have changed in the West Antarctic region over the past 300 years and how this has impacted the regional climate. The data will provide a much needed record to test the 20th century reanalysis data and the intrinsic variability of climate models currently used to predict future climate change in this region,including the impact on ocean upwelling (and CO2 cycling) and sea level rise.
We identify several key beneficiaries
1. Academic researchers: (e.g. Palaeoclimatologists, oceanographers, glaciologists, climatologists and climate modellers) who are researching Antarctic climate variability, oceanic circulation and upwelling in the Amundsen/ Bellingshausen Sea or Antarctic mass balance and sea level rise.
2. Intergovernmental Panel on Climate Change (IPCC). The IPCC is by far the most influential group synthesising and delivering climate research and projections to policy-makers. A key goal of the next IPCC report will be to produce improved predictions of how the West Antarctic Ice Sheet will change over the next century and thus our data, and the subsequent research conducted by our academic beneficiaries, will contribute to this aim.
3. With huge public interest in Antarctic climate change we anticipate our results will be of interest to the television and press, and we will issue press releases to coincide with the publication of our major papers and undertake outreach and educational activities at local schools and science fairs.

Publications

10 25 50
 
Description Climate variability in coastal West Antarctica The annual average deuterium isotope record, providing a record of climate variability in coastal West Antarctica back to 1703, is now published in Geophysical Research Letters http://onlinelibrary.wiley.com/doi/10.1002/2013GL057782/abstract The record revealed that climate variability in coastal West Antarctica is strongly driven by sea surface temperatures and atmospheric pressure in the tropical Pacific. The region warmed since the late 1950s at a rate similar to that observed in the Antarctic Peninsula and central West Antarctica. However, this recent warming trend is similar in magnitude to warming and cooling trends that occurred in the mid-nineteenth and eighteenth centuries, indicating that in this coastal West Antarctic location the effects of human-induced climate change in recent years have not exceeded natural climate variability over the past 300 years.

Diatom sample preparation is now complete for the Ferrigno ice core and Jurassic ice core (308-years). The first paper presenting the first evidence that diatoms are a proxy for southern ocean winds is submitted (Scientific reports). A second paper is in preparation demonstrating that winds have increased during the 20th century, coincident with the increased warming and increased snowfall, however there is evidence of stronger winds during the mid 18th century. Expected submission summer 2018.

The amount of snowfall in the Southern Antarctic Peninsula and West Antarctica has increased dramatically during the 20th century. Values during 1990's higher than at anytime in previous 300 years. Finding presented in http://onlinelibrary.wiley.com/doi/10.1002/2015GL065750/abstract

First 300 year record of sea ice variability in the Amundsen-Ross sea. Evidence for dramatic increase in variability during late 20th century (10.1002/2016GL068130).
Exploitation Route The results have already been taken forward by myself and others. Multiple co-author papers using data gathered from this study including mass balance, tropical teleconnections and sea ice.
Sectors Education,Environment

 
Description In media and public engagements. Media: Discussed in an Open University film for their Environment (journeys through the world) documentary. Contributed to poetry (compiled by Andrew Motion) aired on BBC radio 4. Public engagement: As head of the ice core group I am asked to converse with a wide range of people who visit the ice core labs. This year "non-academic" visits have included, politicians, poets and local business leaders.
First Year Of Impact 2015
Sector Education,Environment,Culture, Heritage, Museums and Collections
Impact Types Societal

 
Description Antarctic mass balance 
Organisation Shandong University
Department School of Computer Science and Technology
Country China 
Sector Academic/University 
PI Contribution Snow accumulation records gathered by this project have been used in several further studies investigating surface mass balance.
Collaborator Contribution Papers led by international partners
Impact Three papers (10.1175/JCLI-D-15-0642.1), (10.5194/tc-10-271-2016) and Review of regional Antarctic snow accumulation over the past 1000 years (submitted).
Start Year 2014
 
Description Antarctic mass balance 
Organisation Utrecht University
Country Netherlands 
Sector Academic/University 
PI Contribution Snow accumulation records gathered by this project have been used in several further studies investigating surface mass balance.
Collaborator Contribution Papers led by international partners
Impact Three papers (10.1175/JCLI-D-15-0642.1), (10.5194/tc-10-271-2016) and Review of regional Antarctic snow accumulation over the past 1000 years (submitted).
Start Year 2014
 
Description Collaborative analysis with National Isotope Laboratory 
Organisation Natural Environment Research Council
Department NERC Isotope Geosciences Laboratory
Country United Kingdom 
Sector Academic/University 
PI Contribution Two proposals for isotope analysis (directly funded by NERC as part of research grant NE/J020710/1).
Collaborator Contribution Isotope analysis.
Impact Provided data to contribute to publications.
Start Year 2013
 
Description PAGES Antarctica 2K consortium 
Organisation PAGES (Past Global Changes)
Department Antarctica2k
Country Switzerland 
Sector Charity/Non Profit 
PI Contribution The data collected as part of this proposal is being used to improve our understanding of the global climate during the past 2000 years. PI Thomas is on the steering committee of the Antarctica2K consortium. Presenting results at international meetings and conferences and co-authoring a collaborative publication.
Collaborator Contribution Forming a network of researchers, collaboration and data sharing for community publications and presentations.
Impact Multi-disciplinary and international.
Start Year 2015
 
Description Sea ice variability 
Organisation University of Tasmania
Department Menzies Institute for Medical Research
Country Australia 
Sector Hospitals 
PI Contribution Data gathered as part of this project used to investigate winder Antarctic sea ice variability. Contributed data, ideas and text for publications.
Collaborator Contribution Led on papers
Impact Paper (doi:10.1002/2016JC012111)
Start Year 2016
 
Description Tropical and subtropical teleconnections 
Organisation University of New South Wales
Country Australia 
Sector Academic/University 
PI Contribution Isotope and snow accumulation data gathered from this project contributed to further publications investigating tropical teleconnections. Contributed data, ideas and text for papers.
Collaborator Contribution Led on paper writing
Impact Paper (doi:10.5194/cp-2016-114) and presentations (SCAR conference 2016).
Start Year 2016
 
Description Article in International Innovation 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact Article in International Innovation, which disseminates the latest research and policy to a global audience.

Requests for information from fellow researchers
Year(s) Of Engagement Activity 2013
 
Description Educational documentary 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Co-presented an Open University documentary "Journey through a changing world"
Year(s) Of Engagement Activity 2016
 
Description Media activity 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Several interviews with international journalists following the publication of "Twentieth century increase in snowfall in coastal West Antarctica".
It was syndicated widely across news outlets in the US, Asia, South Africa and South America - 114 news items in total online (Nov 2015). This included Discovery Channel news online with over 4 million unique monthly visitors and Science Daily with over 10 million visitors per month.


Ongoing invitations for interviews. Increased paper downloads.
Year(s) Of Engagement Activity 2015,2016
URL http://wiley.altmetric.com/details/4720359
 
Description Poetry collaboration - Andrew Motion 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Contributed to poetry "voices of the earth" aired on BBC radio 4 following engagement with poet Andrew Motion
Year(s) Of Engagement Activity 2016