Icebergs, meltwater and the overturning circulation during Marine Isotope Stage 6

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• Mattias Green (Bangor University)
• Wednesday 09 February 2011, 11:00-12:00
• British Antarctic Survey, Room 330B.

If you have a question about this talk, please contact Povl Abrahamsen.

Scour marks on the Lomonosov Ridge in the central Arctic Basin imply that icebergs with drafts exceeding 850 m once existed in the Arctic, and the most likely source of such bergs is the disintegration of the Barents Ice Sheet during Marine Isotope Stage 6 (MIS 6; 140 ka BP). Here, an intermediate complexity climate model is used to simulate the collapse of the Barents Ice Sheet during MIS 6 to investigate the drift patterns of icebergs originating from the Barents ice sheet, and what the implications of the associated freshwater input were for the ocean circulation. The simulations show that deep-draft bergs seeded from the Franz Victoria Trough could indeed have reached the Lomonosov Ridge, whereas other bergs crossed the Yermak Plateau and exited through the Fram Strait. This work is consistent with previous speculation regarding the origin of the icebergs, but suggests an origin from the western, rather than eastern, major ice stream of the Barents ice sheet. Furthermore, the collapse of the Barents Ice Sheet had a significant impact on the ocean circulation. Freshwater fluxes of 0.15 Sv and iceberg surges of 0.1 Sv applied over 500 years trigger significant changes in the global overturning circulation, particularly in the North Pacific Ocean, where there is strengthening of the overturning at the expense of that in the North Atlantic, and increases in air and sea surface temperatures. These results highlight the importance of simulating not only the correct flux but also the form of the freshwater input from ice-sheet collapses appropriately.

This talk is part of the British Antarctic Survey - Polar Oceans seminar series series.

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