How Antarctic winds shaped CO₂

What SIWHA does

SIWHA investigates how westerly winds and sea ice have influenced CO2 uptake and release in the Southern Ocean.

The project involves drilling an ice core spanning ice core spanning recent centuries in the Antarctic Peninsula. Analyses combine traditional and novel ice core proxies to study past climate and atmospheric CO2.

Why this matters

Westerly winds and sea ice play a key role in regulating Southern Ocean CO2 exchange. Understanding their past variability helps reveal natural climate patterns and long-term carbon cycling.

This knowledge improves predictions of how Antarctic processes may influence global climate under future warming.

How the project works

SIWHA uses ice core and climate analyses to study decadal to millennial-scale processes:

• Ice core drilling: collects a ~300m ice core from the Antarctic Peninsula spanning the Holocene.
• Proxy analysis: measures westerly wind strength, sea ice extent, and atmospheric CO2 using chemical and isotopic indicators.
• Temporal study: examines variability from pre-industrial times to the present.
• Climate linkages: investigates connections between Antarctic winds, sea ice, and extratropical or tropical climate modes.

Science objectives

The project aims to:

• quantify variability of westerly winds and sea ice in the Pacific sector of the Southern Ocean
• measure atmospheric CO2 over the Holocene at multi-decadal resolution
• determine how winds and sea ice influence CO2 concentrations
• identify long-term linkages with regional and global climate modes
• provide a detailed record of Antarctic climate dynamics over past centuries

Who is involved

SIWHA is a Natural Environment Research Council (NERC)-funded project led by BAS scientists, supported by ice core specialists and international climate research collaborators.

Scientific rationale

The Southern Ocean currently absorbs over 40% of the anthropogenic carbon dioxide (CO₂) and 75% of the anthropogenic heat from the atmosphere. However, the Southern Ocean can also release CO₂. The extent to which the ocean will act as a source or sink of anthropogenic CO₂ in the future is unknown. This constitutes one of the biggest uncertainties facing society today. The SIWHA project will be a breakthrough in our understanding of CO₂ exchange in the Southern Ocean. Determining how westerly winds and sea ice have influenced the uptake or release of CO₂ at decadal to millennial timescales.

Project plan and deliverables:

1. Geophysical survey and ice core drilling

Conduct geophysical surveys (November 2024) to identify the most suitable site for deep drilling. Measure bed topography, englacial stratigraphy, ice rheology, and ice-flow fields. Directly measure past ice deformation during burial to constrain the ice core age-scale. Use the BAS electromechanical deep drill to reach bedrock ~800 m (2025/2026).

2. Wind reconstructions

Marine diatoms  are unicellular algae with siliceous cell walls. Diatoms are uplifted from the sea-surface microlayer and transported by winds over the ice sheet. The diatom abundance measured in an ice core is dependent on the strength of the winds. We will use this diatom abundance as a proxy to reconstruct past wind strength and atmospheric circulation. We will also use traditional wind proxies,  including dust and continental ions.

3. Greenhouse gas analysis

The new high snow accumulation ice core will provide the first complete record of greenhouse gases (carbon dioxide and methane) spanning the entire Holocene (>11,000 years). The analysis will be completed in the newly developed UK Relic Air Extraction and Gas Analysis System (UK RArE-GAS) laboratories at BAS. The bubble close-off at this site is very rapid. Providing a unique opportunity to measure gas records that overlap with the instrumental data.

1. Ice Core Gas Lab

   Specialist ice core facility to measure concentration and isotopic composition of greenhouse gases

   Read more of: Ice Core Gas Lab

   

2. Ice core aquisition and analysis

   UK national facility and capability

   Read more of: Ice core aquisition and analysis