The influence of the Arctic sea ice extent variability over the northern South American precipitation

Abstract

The arctic sea ice is presenting unprecedent retreat and some research state that the arctic region is warming three to four times faster than the rest of the world. At the same time, middle latitudes have experienced extreme events such as extreme snow fall and episodes of extreme low temperatures which some literature suggest that are connected to the arctic warming. In this thesis we explore teleconnections between the arctic and the tropics, most specifically northern South America (nSA). For this analysis we have two objectives: exploring how the arctic sea ice decline could influence the precipitation over nSA, and second, using two PAMIP models scenarios to explore future impacts of the arctic sea ice loss over the precipitation in nSA. Firstly, using sea ice data provided by NSIDC and precipitation monthly means reanalysis data for the same period provided by NCEP/NCAR, we correlate precipitation anomalies in equatorial South America with Arctic sea ice extent anomaly series. A precipitation center with the highest correlation with Arctic sea ice extent anomalies was identified in the eastern part of equatorial South America (in the Amazon rainforest). This region's time series was then compared to the sea ice extent anomaly using a linear regression dependence analysis. An rsquare of 15% was found; in other words, the sea ice variability might influence 15 percent of the precipitation volume anomaly in some parts of Brazil’s northern and northeastern regions. Secondly, we used five models from the PAMIP to quantify the precipitation changes over nSA using two different scenarios, one employing present-day SST and sea ice concentration (SIC) and other consisting in projections of the SIC in the Arctic considering 2°C atmospheric warming relative to pre-industrial conditions. The model average projections for the DJF season show drier conditions in the northern part of the Amazon and wetter conditions in the southern part in the >2 °C scenario. At the same time, the JJA season shows wetter conditions in the western part of the Amazon region, and drier conditions in the eastern part. These precipitation changes are related to changes in the atmospheric circulation in the tropical Atlantic.