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The Southern Ocean's biological pump during the Last Glacial Maximum


Anderson, RF and Chase, Z and Fleisher, MQ and Sachs, J, The Southern Ocean's biological pump during the Last Glacial Maximum, Deep-Sea Research Part 2: Topical Studies in Oceanography, 49, (9-10) pp. 1909-1938. ISSN 0967-0645 (2002) [Refereed Article]

Copyright Statement

Copyright 2002 Elsevier Science Ltd.

DOI: doi:10.1016/S0967-0645(02)00018-8


Ice core records from Antarctica show large (∼80 ppm) and regular climate-related changes in atmospheric CO2, with minimum values during glacial periods and maximum values during peak interglacials. The suggested role of the Southern Ocean in driving these changes is based on either the potential for increased utilization of surface nutrients or the potential for decreased ventilation of deep waters during glacial times. Several recent studies have invoked increased stratification of the Southern Ocean to explain lower glacial atmospheric CO2 levels in terms of reduced exchange of CO2 between the deep sea and the atmosphere. A northward displacement and/or substantial weakening of the westerly winds during glacial periods are implicit in the scenarios that invoke enhanced stratification. However, both circulation models and proxy results argue against a weakening of the westerlies. In fact, the mean flow of the Antarctic Circumpolar Current and wind-driven upwelling during the Last Glacial Maximum (LGM) are thought to be at least as vigorous as those which exist today. Given these boundary conditions, we offer two (competing) scenarios for ecosystem structure and export production of the glacial Southern Ocean. The first scenario satisfies all proxy records for nutrient utilization and phytoplankton growth rate, and requires increased (relative to today) nitrate utilization south of the Antarctic Polar Front (APF) by phytoplankton other than diatoms, together with a shift in the zone of maximum diatom growth from south (interglacials) to north (glacials) of the APF. The second scenario has reduced growth of all phytoplankton species south of the APF during glacials, and a shift in the zone of maximum export production to the north of the Polar Front. The principal weakness of the first scenario is that there is little sedimentary evidence to support the increased export of particulate organic carbon required by the inferred increase in nitrate utilization south of the APF. The principal weakness of the second scenario is that it requires a change in the isotopic fractionation of nitrogen by phytoplankton growing south of the Polar Front for reasons presently unknown. The Southern Ocean's biological pump at the LGM has yet to be characterized unequivocally.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Physical geography and environmental geoscience
Research Field:Palaeoclimatology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Chase, Z (Professor Zanna Chase)
ID Code:101463
Year Published:2002
Web of Science® Times Cited:107
Deposited By:IMAS Research and Education Centre
Deposited On:2015-06-24
Last Modified:2015-08-31

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