Past behaviour of polar oceans and their role as drivers of future climate change

Stormy seas in the Drake Passage.

Palaeoceanographers, palaeoclimatologists and geochemists have become increasingly aware that processes occurring in the Southern Ocean play a major role in the Earth’s climate system. The importance of the Southern Ocean stems from its circumpolar location and its role in the formation and modification of deep and bottom waters.

Comprising the southern-most basins of the Atlantic, Indian and Pacific Ocean, the Southern Ocean provides the principal connection between the oceans and is therefore central to global ocean circulation. Northern and southern sourced waters are transported through the Southern Ocean via the Antarctic Circumpolar Current (ACC). Driven by the intense southern westerly winds (SWW) of the mid-to-high latitudes, the ACC not only provides unique connectivity between the ocean basins but also brings strong atmospheric links.

The Southern Ocean’s circumpolar location also supports the largest seasonal change on earth – the expansion/retreat of seasonal sea-ice. In contrast to the Arctic, Antarctic sea-ice expansion is uninhibited by landmasses and each winter grows to double the continental area of Antarctica. This sea-ice migration is an important component of climate, initiating powerful feedbacks associated with surface albedo (the amount of solar energy reflected), ocean-atmosphere gas-energy exchange and biogeochemical processes. The respective addition of salty and fresh water during sea ice formation and melting also contribute important characteristics to Antarctic water masses and create niche environments that comprise an important feature of the Antarctic marine ecosystem.

We use and develop fossil and geochemical proxies to reconstruct ocean conditions on a range of timescales to assess how the Southern Ocean reacts to and impacts regional and global climate.

The role of Antarctic sea-ice in global climate

Sea-ice is frequently cited as a likely driver and propagator of abrupt climate change because of the rapid and far-reaching impact of its feedbacks. However, numerical climate models are still …