Evaluation of trends and analysis of air temperature and wind on the Antarctic Peninsula using Extreme Value Theory

Abstract

Abstract The west side of the Antarctic Peninsula (AP) shows both warming and cooling since the middle of the last century, however is more characterized by warming because of the disintegration of floating ice and strength of westerly winds. Two climatic databases (reanalysis from 1979 to 2020 and surface stations from 1947 to 2020) are analyzed to investigate trends in extreme air temperatures and wind components in west, east sector and over the AP. Non-parametric statistical trend tests and extreme value approaches are used. A set of annual, monthly and seasonal series are fitted. The extremal index is applied to measure the degree of independence of monthly excesses over a threshold considered as extreme events. Increasing trends are verified in the annual and monthly temperature and wind series. The greatest trends are observed for seasonal series from reanalysis without change-point in summer and winter. Decreasing trends are observed for maximum temperature in summer and positive trends mainly for the westerly winds over the AP. But in winter, the maximum temperature shows an increase trend also over the AP. Most of reanalysis seasonal minimum temperature and wind components, as well as maximum and minimum temperatures from stations present increasing trends with change-point but, tending to stability after the breakpoints. The generalized distribution (GEV) is used to fit temperatures and westerly wind between South America (SA) and north of the AP. The 100-years return levels exceed the maximum value of the maximum temperature in Esperanza and maximum westerly winds at several grid points. Pareto and Poison distributions are applied for the maximum temperatures from stations and the 100-year return levels are not exceeded. Our findings show significant positive trends for monthly wind components near the SA in the region of the westerly winds whose changes in position influence directly the SAM, which modify the atmospheric patterns in the South Hemisphere (SH). A predominance of seasonal warming is identified, which may impact the climate with consequences not only locally but also in other region.