613 Seminar: Bradley M. Hegyi

USRA-NPP/Langley Research Center

In recent decades, the Arctic surface and lower troposphere has warmed at twice the rate as the global average, in a process termed Arctic amplification, with the peak amplification occurring in fall and winter.  Additionally, over the same time period, the thickness of fall and winter sea ice has thinned, increasing the sensitivity of the growth of sea ice to atmospheric and oceanic perturbations.  Given that the trend towards thinner sea ice and Arctic amplification is predicted to continue in climate model projections, with much spread between different models, it is important to understand what drives recent Arctic amplification and sea ice growth variability to improve future climate model predictions of Arctic climate.
The talk presented will highlight the link between atmospheric variability, surface temperature variability, and Arctic sea ice growth in fall and winter, in the context of last year’s record-setting Arctic sea ice growth season (2016-17).  A key mechanism that facilitates the link is the transport of relatively warm and moist air from lower latitudes, termed moisture intrusions. The impact of moisture intrusions is twofold. First, the presence of a moisture intrusion increases amount of energy transferred by downwelling longwave fluxes at the surface, resulting in significant increases in Arctic surface temperatures and reduced sea ice growth.  The associated increased downwelling longwave flux increase occurs primarily through increased clear-sky fluxes and secondarily through an increased longwave cloud radiative effect. Second, the presence of a moisture intrusion reduces the efficiency by which the surface cools radiatively to space by upwelling longwave fluxes.  The case study of the past winter of 2016-17 will show how multiple moisture intrusions contributed to record warm October-February-average Arctic surface temperatures and record low sea ice volume and extent at the end of the winter season.
Seminar Series Coordinators