Wind‐Driven Evolution of the North Pacific Subpolar Gyre Over the Last Deglaciation
International audience North Pacific atmospheric and oceanic circulations are key missing pieces in our understanding of the reorganization of the global climate system since the Last Glacial Maximum. Here, using a basin-wide compilation of planktic foraminiferal δ 18 O, we show that the North Pacif...
Published in: | Geophysical Research Letters |
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Main Authors: | , , , , , , , |
Other Authors: | , , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2020
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Subjects: | |
Online Access: | https://hal.science/hal-02968755 https://hal.science/hal-02968755v1/document https://hal.science/hal-02968755v1/file/2019GL086328.pdf https://doi.org/10.1029/2019GL086328 |
Summary: | International audience North Pacific atmospheric and oceanic circulations are key missing pieces in our understanding of the reorganization of the global climate system since the Last Glacial Maximum. Here, using a basin-wide compilation of planktic foraminiferal δ 18 O, we show that the North Pacific subpolar gyre extended~3°further south during the Last Glacial Maximum, consistent with sea surface temperature and productivity proxy data. Climate models indicate that the expansion of the subpolar gyre was associated with a substantial gyre strengthening, and that these gyre circulation changes were driven by a southward shift of the midlatitude westerlies and increased wind stress from the polar easterlies. Using single-forcing model runs, we show that these atmospheric circulation changes are a nonlinear response to ice sheet topography/albedo and CO 2. Our reconstruction indicates that the gyre boundary (and thus westerly winds) began to migrate northward at~16.5 ka, driving changes in ocean heat transport, biogeochemistry, and North American hydroclimate. Plain language summary Despite the North Pacific's importance in the global climate system, changes in the circulation of this region since the last ice age are poorly understood. Today, the North Pacific Ocean has distinct properties north and south of~40°N: To the south, the warm surface waters form a circulation cell that moves clockwise (the subtropical gyre); to the north, the cold surface waters form a circulation cell that moves anticlockwise (the subpolar gyre). This difference in surface ocean circulation north and south of~40°N is determined by the wind patterns. Here, using a compilation of oxygen isotopes measured in the carbonate shells of fossil plankton from sediment cores across the basin, which tracks changes in the spatial pattern of temperature, we reconstruct how the position of the boundary between the gyres changed since the last ice age. Our results show that the boundary between the gyres was shifted southward by~3°during the last ... |
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