Retreat of Southern Hemisphere Sea Ice, 130 000 to 116 000 years BP

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

Abstract

Sea ice is of huge importance to global climate, the Antarctic ice sheet, and to all life in the Southern Ocean. However the area covered by sea ice in the Southern Hemisphere is predicted to drastically decrease over the next century; the decrease by 2200 could be as much as 58%.

The models, on which predictions of sea ice loss are based, have never been tested against a documented retreat of Southern Hemisphere sea ice. A major retreat in Northern Hemisphere sea ice since 1978 has enabled climate and sea ice models to be evaluated for their ability to replicate retreat data. This has helped ensure that we have high confidence in Arctic sea ice predictions. In the Southern Hemisphere, there has been no similar sea retreat since 1978, which has meant that models cannot be tested against retreat data. This lack of sea ice retreat data has thus been a major contributor to the current lack of confidence in Southern Hemisphere sea ice forecasts.

Here we propose to address this lack of data which covers a retreat of the Southern Hemisphere sea ice. We have found a period during the Last Interglacial (LIG) between 130,000 and 116,000 years Before Present (BP), when there was a substantial retreat in Southern Hemisphere sea ice. By reconstructing and modelling a retreat during this LIG period, under a climate which was similar to that of today, this proposal aims to transform understanding of the structure and causes of a major Southern Hemisphere retreat event. The project will be the first ever quantitative investigation of a large Southern Hemisphere sea ice retreat, and will be be of considerable importance to both the sea ice and palaeoclimate science communities.

We will generate a new LIG sea ice dataset, using a robust new statistical approach. This will draw from, and build upon, the core expertise of our science team members. Our new Southern Hemisphere sea ice data data will then be used to help establish the cause of the LIG retreat and to test current climate and sea ice models. In addition to identifying the most likely cause of the decrease in sea ice during the LIG, this project will establish for the first time the degree of confidence that the sea ice community can have in our UK model-based predictions of a future retreat in Southern Hemisphere sea ice.

Planned Impact

WHO WILL BENEFIT FROM THIS RESEARCH?
Target audiences who will benefit from this research are: palaeoclimate and sea ice scientists (the main beneficiaries of the research as detailed in the above `Academic beneficiaries' section) as well as stakeholders (with a focus on policy-makers) and the general public (with a strong emphasis on schoolchildren at key stage 1 and 2).

The main users of the research outcomes who are outside of the immediate research community will be policy-makers and their science advisors. In particular, the Scientific Committee on Antarctic Research (SCAR) and the International Panel on Climate Change (IPCC) use evidence on polar and climate change to gauge the severity of anthropogenically enhanced global warming to help policy-makers develop an appropriate level of response.

HOW WILL THEY BENEFIT FROM THIS RESEARCH?
POLICY-MAKERS. Submission of our previous publications to the appropriate IPCC AR5 Chapter editors ensured that our work forms part of past IPCC reports, thereby influencing UK and global policy. As an example of this influence, if this proposed research were to demonstrate that the UK Coupled Model Inter-comparison Project (CMIP6) Climate Model predictions of Southern Hemisphere sea ice changes are likely to be underestimated, it would increase the urgency for action proposed by SCAR and the IPCC. Similarly, if Southern Hemisphere sea ice changes are overestimated, this may allow attention to be focussed elsewhere.

CHILDREN AND TEACHERS. We hope to engage and inspire children with the spirit of Antarctic scientific endeavour - these young people will go on to become the future scientists and decision makers for NERC and for Antarctica. We propose to partner with the charity UK Antarctic Heritage Trust to produce inspirational resources for schools. The Antarctic Heritage Trust are dedicated to caring for, and promoting, Antarctic scientific heritage. Together, we will create a variety of learning resources based jointly on Trust archival material and our contemporary research outcomes. This approach will build on previous Trust successes in producing and distributing school resources. The learning resources will be aimed at teachers and pupils in schools to use in the classroom. A combination of digital and print resources will be written with the aid of a freelance educational specialist. The digital resources will be made freely available through existing child and teacher friendly sites, including show.me.uk and mylearning.org along with the tried and tested discoveringantarctica.org.uk website. Printed resources will be particularly targeted at less privileged schools.

PRESSURE GROUPS / CLIMATE SCEPTICS. We will write at least one project RealClimate (www.realclimate.org) project blog post to reach the 'climate sceptic' pressure groups. The post will be co-written with the sea ice modellers Prof. D. Feltham and Dr. D. Schroeder. Post(s) will directly address a major line of attack on climate science: "Increases in Southern Hemisphere sea ice, particularly since 2012, undermine evidence for global warming". By talking with these users, using their own preferred means of communication, we will work to minimise the potential for any misunderstanding of Southern Hemisphere sea ice science.

LOCAL SCHOOLS, WI, AND U3A AUDIENCES. We will build on our record of public lectures by providing three public lectures per year of the project.

MEDIA AND THE GENERAL PUBLIC. Press releases, twitter, and a project web page will be used to both encourage and satisfy public interest in the work.

Publications

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Holloway M (2017) The Spatial Structure of the 128 ka Antarctic Sea Ice Minimum in Geophysical Research Letters

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Sime LC (2019) Impact of abrupt sea ice loss on Greenland water isotopes during the last glacial period. in Proceedings of the National Academy of Sciences of the United States of America

 
Description Our ice core-model comparison indicates a last interglacial maximum winter sea ice retreat of 67, 59, and 43% relative to preindustrial in the Atlantic, Indian, and Pacific sectors of the Southern Ocean. Our compilation of Southern Ocean sea ice proxy data provides support for this ice core based reconstruction. We find that published marine core sites are located too far north of the 128,000 years B.P. sea ice edge, preventing independent corroboration for this sea ice reconstruction. These results may have had serious implications for the stability of marine terminating glaciers around the Antarctic Ice Sheet and their contribution to the last interglacial sea level rise. Further we demonstrate that climate models are capable of simulating this sort of sea ice retreat when run for 2-3000 years under norther hemisphere meltwater forcing.
Exploitation Route These finding are primiarily of use to the sea level community.
Sectors Energy,Environment,Government, Democracy and Justice,Security and Diplomacy

URL https://www.bas.ac.uk/data/our-data/publication/the-spatial-structure-of-the-128-ka-antarctic-sea-ice/
 
Description Outreach through Maker Workshops.
First Year Of Impact 2019
Sector Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal

 
Description EPSRC-PEN feasibility study
Amount £8,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2017 
End 12/2017
 
Title Southern Hemisphere winter sea ice concentration simulated by HadCM3 to best explain the early last interglacial Antarctic isotope peak 
Description The file contains Southern Hemisphere winter (September) sea ice concentration (sic) from a simulation performed using the isotope-enabled HadCM3 climate model forced with early last interglacial boundary conditions, centred approximately 128,000 years ago. The resulting sic represents a reduction in winter sea ice area of approximately 54% relative to pre-industrial and is proposed as the best explanation for the Antarctic ice core data from 128,000 years ago. The spatial pattern of sea ice retreat was determined using a large ensemble of model experiments and a pattern search optimization approach to match the last interglacial ice core isotope peak. Further details can be found in the published manuscript (https://doi.org/10.1002/2017GL074594). 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Description Eric J. Steig Professor, Earth & Space Sci. And IsbLab 
Organisation University of Washington
Department Department of Biostatistics
Country United States 
Sector Academic/University 
PI Contribution Provision of Climate Model isotopic output for location of possible US led Hercules Dome ice coring site.
Collaborator Contribution Provision of Climate Model isotopic output for location of possible US led Hercules Dome ice coring site.
Impact Papers in preparation.
Start Year 2016
 
Description The Past Earth Network (PEN) 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution Co-leader of the PEN Model-Data comparison group. Myself and my research group will be helping to organise PEN workshops in the coming years.
Collaborator Contribution Organising conference sessions and PhD studentships: earth sciences and statisticians
Impact Conference sessions and PhD studentships: earth sciences and statisticians
Start Year 2015
 
Description Maker workshops in London 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Free creative workshops using art, crafts and model making to share ideas about responding to the impacts of climate change.

2:30pm 24 January, 21 February, 20 March

The news is full of fires and floods and it is difficult to know how to help. These workshops will imagine and invent ways we can respond to the experience of
climate change in different ways around the world.
Year(s) Of Engagement Activity 2019,2020