Eastern Pacific cooling and Atlantic overturning circulation during the last deglaciation

Kienast, M Kienast, SS Calvert, SE Eglinton, TI Mollenhauer, G Francois, R Mix, AC

NATURE 443:7113 846-849

Surface ocean conditions in the equatorial Pacific Ocean could hold the clue to whether millennial-scale global climate change during glacial times was initiated through tropical ocean - atmosphere feedbacks or by changes in the Atlantic thermohaline circulation(1). North Atlantic cold periods during Heinrich events and millennial-scale cold events (stadials) have been linked with climatic changes in the tropical Atlantic Ocean and South America(2-4), as well as the Indian and East Asian monsoon systems(5,6), but not with tropical Pacific sea surface temperatures(7). Here we present a high-resolution record of sea surface temperatures in the eastern tropical Pacific derived from alkenone unsaturation measurements. Our data show a temperature drop of 1 degrees C, synchronous ( within dating uncertainties) with the shutdown of the Atlantic meridional overturning circulation during Heinrich event 1, and a smaller temperature drop of 0.5 degrees C synchronous with the smaller reduction in the overturning circulation during the Younger Dryas event. Both cold events coincide with maxima in surface ocean productivity as inferred from Th-230-normalized carbon burial fluxes, suggesting increased upwelling at the time. From the concurrence of equatorial Pacific cooling with the two North Atlantic cold periods during deglaciation, we conclude that these millennial-scale climate changes were probably driven by a reorganization of the oceans’ thermohaline circulation, although possibly amplified by tropical ocean - atmosphere interaction as suggested before(8).

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Integration of ice-core, marine and terrestrial records for the Australian Last Glacial Maximum and Termination: a contribution from the OZ INTIMATE group

Turney, CSM Haberle, S Fink, D Kershaw, AP Barbetti, M Barrows, TT Black, M Cohen, T Correge, T Hesse, PP Hua, Q Johnston, R Morgan, V Moss, P Nanson, G Van Ommen, T Rule, S Williams, NJ Zhao, JX D’Costa, D Feng, YX Gagan, MK Mooney, S Xia, Q

JOURNAL OF QUATERNARY SCIENCE 21:7 751-761

The degree to which Southern Hemisphere climatic changes during the end of the last glacial period and early Holocene (30-8 ka) were influenced or initiated by events occurring in the high latitudes of the Northern Hemisphere is a complex issue. There is conflicting evidence for the degree of hemispheric ‘teleconnection’ and an unresolved debate as to the principle forcing mechanism(s). The available hypotheses are difficult to test robustly, however, because the few detailed palaeoclimatic records in the Southern Hemisphere are widely dispersed and lack duplication. Here we present climatic and environmental reconstructions from across Australia, a key region of the Southern Hemisphere because of the range of environments it covers and the potentially important role regional atmospheric and oceanic controls play in global climate change. We identify a general scheme of events for the end of the last glacial period and early Holocene but a detailed reconstruction proved problematic. Significant progress in climate quantification and geochronological control is now urgently required to robustly investigate change through this period. Copyright (c) 2006 John Wiley & Sons, Ltd.

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