Sea Ice and Westerly winds during the Holocene in coastal Antarctica, to better constrain oceanic CO2 uptake

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The Southern Ocean represents less than one-tenth of the area of the global ocean, yet it currently absorbs 43% of the total anthropogenic CO2 and 75% of the heat. Critically, the Southern Ocean's capacity to modulate the atmospheric CO2 concentration is governed by the strength and position of the Southern Hemisphere westerly winds. These winds drive upwelling of carbon-rich deep water, which together with sea ice coverage, determines the ocean surface area available for air-sea gas exchange. Westerly winds are predicted to increase in strength during the 21st century, as a result of anthropogenic forcing, while sea ice is predicted to decrease. The combination of stronger winds over the surface ocean and reduced sea ice cover will enhance upwelling of carbon-rich water from the deep ocean. Thus, the Southern Ocean may switch from a CO2 sink to a CO2 source, potentially releasing CO2 into the atmosphere and accelerating global warming through enhanced radiative forcing.However, our understanding of the role of westerly winds on CO2 release is limited by the short observational records with large uncertainties in the magnitude of projected westerly wind changes in climate models. In order to better constrain future predictions of CO2 emissions and climate change, we urgently require long records of atmospheric CO2, westerly winds and sea ice in the Southern Ocean. Ice cores are the only paleoclimate archive that can reconstruct all three parameters beyond the instrumental period. The aim of this proposal is to provide high resolution records of westerly winds, sea ice and atmospheric CO2 concentrations over multi-decadal to millennial timescales. We will do this by drilling a new ice core in coastal Antarctica, match funded by the National Centre for Polar and Oceanographic Research (NCPOR), Indian Ministry of Earth Science, with additional support secured from the Norwegian Polar Institute and the UK embassy in Delhi. We will conduct state-of-the-art analysis, using newly developed proxies for westerly winds based on marine diatoms. Advanced measurement of the stable isotopic composition of CO2 will take place in the newly established UK Relic Air Extraction and Gas Analysis System (UK RArE-GAS) laboratories and build on the UK's growing expertise in this field.This is an exciting opportunity for UK scientists to collaborate with leading polar research institutes in Norway and India. This tri-national partnership (India/Norway/UK) considerably increases the scientific, societal, and political impact. Disentangling the drivers of CO2 variability over seasonal to millennial scales is essential in predicting future changes in atmospheric CO2 concentrations. If the Southern Ocean switches from a CO2 sink, removing anthropogenic CO2 from the atmosphere, to a CO2 source, releasing CO2 from the deep ocean, is of global concern. Thus, we anticipate this project will have high scientific, political, and social-economic impacts.These social-economic impacts will hit some countries harder than others. India's large coastline and rapidly increasing population, many of whom live in low-lying coastal basins, make it particularly susceptible to future sea level rise. India is the fifth most vulnerable country in the world to the impacts of climate change and is under pressure to reduce its greenhouse gas emissions. Thus, this new collaboration with partners in India provides compelling potential for NERC and UK scientists to support and promote climate science in an ODA country. Working directly with the Indian Ministry of Earth Sciences and facilitated by ongoing collaborations with senior advisor for climate change and environment at the British High Commission in Delhi.