The Roaring 40s: understanding changes in the Southern Hemisphere westerly winds and their impacts

Date & time

1–2pm 3 May 2018

Location

Jaeger 1 Seminar Room, RSES

Speakers

Julie Arblaster (Monash University)

Event series

Contacts

 Adele Morrison

The Southern Hemisphere atmospheric circulation is dominated by the mid-latitude westerlies which encircle Antarctica and drive changes in surface climate as well as the ocean and cryosphere. Given the sparsity of data over the Southern Ocean, observed changes in the position and strength of these winds can also be indicated by the Southern Annular Mode (SAM) which can be defined by contrasting station records of sea level pressure between the mid-latitudes and polar regions. The SAM has a strong influence on the weather and climate of the Southern Hemisphere polar regions as well as southern Australia, New Zealand, southern South America and South Africa. The SAM and westerly winds have shown a significant strengthening and poleward shift in austral summer, which has been attributed primarily to ozone depletion with contributions from increasing greenhouse gases and natural variability. This seminar will discuss recent understanding of how the SAM and westerly winds have varied on year-to-year to longer timescales as well as their impacts on surface climate. Results highlight contributions of the SAM to long-term trends in Southern Hemisphere rainfall and surface temperatures as well as recent record rainfall and temperature extremes over Australia and the extraordinary decline of Antarctic sea ice that began in spring 2016.

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