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Chemistry and Past Climate Programme Summary

A slice of ice core from Berkner Island, depth 120m. Trapped air bubbles - an archive of the past atmosphere - are visible in the ice.
A slice of ice core from Berkner Island, depth 120m. Trapped air bubbles - an archive of the past atmosphere - are visible in the ice.

Science Leader: Dr Robert Mulvaney (rmu@bas.ac.uk)

Introduction

To understand how the Earth and its climate will react to, mitigate, and amplify external changes, we can observe the past and study the present – only then can we predict the future. Important processes in regulating the Earth System take place in or near the polar regions, and the best records for understanding the way the Earth has worked in the past (ice cores) are found there.

The Chemistry and Past Climate programme concentrates on the Quaternary period (the last 2.6 million years). Ice-core and other palaeorecords can be analysed for that period. Although many aspects of the Earth were similar to the present, large climate changes, as well as periods warmer than today, can be observed. BAS scientists investigate how different parts of the Earth System interacted to produce the large climate changes that occurred naturally in the past, and complement this with investigations on how changing sea-ice and ocean conditions affect the present chemistry of the polar atmosphere.

Programme Goals

  • To understand what controlled the timing and strengths of the major climate shifts of the last million years and beyond, particularly the shifts from glacials (ice ages) to interglacial warm periods
  • To use the warmest periods of the last million years to tell us about the likely response of polar regions to future climate change
  • To determine how sea ice responded to past climate change and assess how this fed back into atmospheric chemistry and ocean circulation
  • To produce detailed records of climate change in the Antarctic Peninsula region over the last 2000 years
  • To produce records of the variation in climate and ocean properties in the Antarctic Peninsula/Filchner-Ronne sector of Antarctica over the last 40,000 years, and reveal the bi-polar pattern of change
  • To quantify how the sea ice zone contributes to regional and global burdens of bromine and iodine compounds; and to quantify how the polar tropospheric ozone and global oxidising capacity are affected by these emissions
  • To determine the variability of CO2 and O2 over the Weddell Sea region, to understand the role of this region in determining past and future CO2 feedbacks

Delivering the Results

The Chemistry and Past Climate programme will address questions about major climate changes of the past using data from ice cores from the European Project for Ice Coring in Antarctica (EPICA), Berkner Island and James Ross Island that we already have. It will drill new ice cores on the Antarctic Peninsula to examine the last 2000 and 40,000 years. This work will be enhanced by new marine cores from the Weddell Sea and Scotia Sea; and lake sediment records from the Antarctic Peninsula and sub-Antarctic islands.

Photo
Graph showing temperature variation at Dome C over 800,000 years

BAS will be partners in the North Greenland Eemian Ice Drilling (NEEM) project, which will complete the record of the last interglacial in Greenland. BAS scientists will also contribute to geophysical survey work to find a site for the proposed “oldest ice” core in Antarctica.

Sensitive instruments deployed at Halley station will measure CO2 and O2, in order to understand the role of the upwind oceanic surfaces in modifying CO2 uptake and release.

The Chemistry and Past Climate programme interpretation of ice core records will include climate and atmospheric modelling studies, aimed both at improving ice core proxies, and understanding the couplings and interactions between different parts of the system. It aims to understand potential sea ice proxy records in ice cores using experimental studies both in the laboratory and in the field, as well as modelling work, to test ideas about sea salt generation.

Atmospheric studies will be extended to determine how sea salt aerosol and sea ice surfaces affect the production of bromine and iodine compounds. These compounds may act as important atmospheric chemistry reactants, and affect polar tropospheric ozone. They are also involved in oxidation of sulphur compounds in the atmosphere, which links the work to another potential sea ice proxy, methanesulfonic acid. The Chemistry and Past Climate programme will use field measurements to strengthen our understanding of the consequences of this production at regional scale; while modelling experiments will assess their effects at regional and global scale.

National and International Context

BAS has a leading role in the International Partnerships in Ice Core Sciences (IPICS), which is endorsed by both the International Geosphere-Biosphere Programme - Past Global Changes (IGBP-PAGES); and the Scientific Committee on Antarctic Research (SCAR). All of the work related to ice cores is within the context and aims of the priority projects defined by IPICS.

Programme information

Science Leader:
Eric Wolff (ewwo@bas.ac.uk)

Related NERC Science Themes:
Earth system science
Climate system

The NEEM Greenland drilling, and the reconnaissance work for oldest ice, will be done with many international partners. Syntheses of climate changes from our synchronised palaeorecords of the climate and glacial history of Antarctica will contribute to the SCAR Antarctic Climate Evolution (ACE) programme, and to regional studies promoted by IGBP-PAGES.

The main UK expertise and capability in ice core science is at BAS; while the Clean Air Sector Laboratory (CASLab) at Halley, and our work there, is the major UK resource for Antarctic atmospheric chemistry. Atmospheric chemistry work is linked to the International Geosphere-Biosphere Programme - International Global Atmospheric Chemistry (IGBP-IGAC) task Air-Ice Chemical Interactions (AICI), in which BAS also plays a leading role.

The Chemistry and Past Climate programme contributes mainly to NERC’s Science Themes on Earth System Science and Climate System. It addresses, in particular, the Earth System Science sub-challenges on using past environments to understand the operation of the Earth System; and on atmospheric composition.

Glossary of terms
Ice cores
Cylinders of ice drilled from a glacier or ice sheet, containing layered sequences of compressed snowfall
Troposphere
The lowest part of Earth’s atmosphere, extending to about 11 km height in the tropics, but less at the poles.
Proxies
Something measured (in an ice or sediment core) that can be interpreted in terms of a variable of interest. In ice cores, changes in the ratios of different water isotopes can be translated into changes in temperature: the isotopes are a proxy for temperature.
Coupling
Many studies consider different components of the Earth, such as the atmosphere and ocean, separately; coupling enables them to be looked at together, with each influencing the other.