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Universitat Autònoma de Barcelona
Institut de Ciència i Tecnologia Ambientals (ICTA-UAB)

OCEAN SEMINAR SERIES: "Poleward shift in the Southern Hemisphere westerly winds synchronous with the deglacial rise in CO2", by Dr William Gray

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Detalles del evento

We are glad to inform that Dr William Gray, research scientist in the Palaeoceanography group at LSCE, France, will be giving an online seminar next Thursday February 30th 2023. The seminar is organised in the framework of the Ocean Seminar Series. These events are part of the Societal Challenge Oceans of María de Maeztu Unit of Excellence (MdM).

 

OCEAN SEMINAR SERIES
 

Title: “Poleward shift in the Southern Hemisphere westerly winds synchronous with the deglacial rise in CO2

Speaker: Dr William Gray, LSCE, France.


Date: Thursday, March 30th, 2023
Time: 1pm
Online: 
https://us06web.zoom.us/j/84730918253?pwd=UzBOenlwNGd3QmJ4WlhaR1MzRmlQZz09


The Southern Hemisphere westerly winds influence deep ocean circulation and carbon storage. While the westerlies are hypothesised to play a key role in regulating atmospheric CO2 over glacial-interglacial cycles, past changes in their position and strength remain poorly constrained. I will present recent work which combines planktic foraminiferal d18O and ‘emergent relationships’ from an ensemble of climate models to reconstruct changes in the Southern Hemisphere westerlies over the last deglaciation. We find a 4.7° (2.9-6.9°, 95% confidence interval) equatorward shift and about a 25% weakening of the westerlies during the Last Glacial Maximum (about 20,000 years ago) relative to the mid-Holocene (about 6,000 years ago). Our reconstruction shows that the poleward shift in the westerlies over deglaciation closely mirrors the rise in atmospheric CO2. Experiments with a 0.25° resolution ocean-sea-ice-carbon model demonstrate that shifting the westerlies equatorward reduces the overturning rate of the ocean deeper than 2 km, leading to a suppression of CO2 outgassing from the Southern Ocean. Our support a role for the westerly winds in driving the deglacial CO2 rise, and suggest natural CO2 outgassing from the Southern Ocean is likely to increase as the westerlies shift poleward due to anthropogenic warming.

Bio

Dr William Gray (@willerstorfi) is a research scientist in the Palaeoceanography group at LSCE, France. He uses the chemical composition of foraminifera (small marine calcifiers) to understand past climate change, and carbonate production and export in the world's oceans. His work includes understanding how we can use Mg/Ca as an accurate paleothermometer, using boron isotopes to understand the ocean's role in driving glacial-interglacial changes in CO2, and using climate models to look at changes in atmospheric and surface ocean circulation over deglaciations.

WILLIAM GRAY