Wind speed variability over the South Shetland Islands, 1988-2019: the relationship between easterlies winds and SAM

Abstract

<p>The Antarctic Peninsula is one of the most affected regions in a warming climate. Climate change not only involves rising air temperatures or changing precipitation patterns, but also wind. Over the past few decades, one of the most prominent changes in the near-Antarctic climate has been the southward shift of the westerly winds, associated with a positive trend in the Southern Annular Mode index (SAM). Some studies revealed that the poleward shift of the westerlies results in an increased in the seasonality of the coastal easterlies, concretely an increase in the difference between weak easterly winds in summer and strong easterlies in winter. The assessment and attribution of the variability of the easterly winds that encircle the coastline is crucial due to its influence e.g. (i) in the sea ice formation and export, (ii) a variation in the easterly winds can modify the Antarctic Bottom Water formation and properties, (iii) the heat transport trough the continent. Due to operational challenges of measuring weather data in the Antarctic region, there are few long-terms time series and studies dealing with wind trends and variability. In this work, wind series from 1988 to 2019 from the Spanish Juan Carlos I Base, located in the South Shetland Islands, specifically in Livingston Island , have been used for the first time to fill this research niche. Speed series have been subjected to a robust quality control and homogenization protocol in Climatol. The results of the magnitude, sign and decadal variability of this series have been compared with the same results for the same time period for the data of ERA5 reanalysis, all of them at three time scales: annual, seasonal and monthly. For both observations and ERA5 we investigate the relationship between speed series and SAM.</p>

Holocene deglaciation and glacier readvances on the Fildes Peninsula and King George Island (Isla 25 de Mayo), South Shetland Islands, NW Antarctic Peninsula

“…The SAM is the primary mode of annual to centennial scale variability in atmospheric circulation in the Southern Ocean (Marshall, 2007) and reflects the zonal mean sea level pressure difference between Antarctica (>65°S) and the mid latitudes (40°S); hence, the SAM index is, in effect, a measure of the longitudinal mean SHW strength (Marshall, 2007). Positive SAM phases are associated with lower pressure at higher latitudes, more poleward focussed SHW, with stronger Westerlies in summer and stronger Easterlies in winter over the NAP and SSI (Martin et al, 2021). During the Holocene, stronger and more poleward SHW are thought to be the centennial-to millennial-scale expression of decadal-centennial warming and positive SAM-like conditions (Charman et al, 2018;Moreno et al, 2018Moreno et al, , 2021Perren et al, 2020).…”