Sea surface temperature changes due to polar lows over the Nordic Seas

Abstract

In this study we analyzed possible changes in sea surface temperature (SST) caused by the passage of polar lows. Polar lows are extreme atmospheric phenomena inherent to high latitudes. They develop sea surface wind speeds from 15 m/s up to hurricane force values and are characterized by small sizes (on average, 300 km) and lifetimes (less than two days), which complicates their detection and study. It is assumed that as in case of tropical cyclones, which may considerably lower SST due to intense mixing and entrainment of colder waters to the ocean upper mixed layer, polar lows could similarly influence SST. Moreover, in high latitude areas, where salt stratification may be present instead of temperature stratification, SST may increase due to mixing with a deeper warmer layer. In this study 330 polar lows were analyzed using satellite passive microwave radiometer measurements of SST. As a result, 47 cases were found in which average SST values changed in polar low forcing areas. Out of these cases, in six cases an SST increase of at least 0.5 °С was found, and in fifteen cases an SST decrease of at least 0.5 °С was found. This indicates that upper ocean response to polar lows is quite a rare phenomenon, which should be further analyzed along with its possible role in the ocean-iceatmosphere system.