Title:	Arctic atmospheric variability and its implication on the summer sea-ice melt
DNr:	SNIC 2014/1-244
Project Type:	SNIC Medium Compute
Principal Investigator:	Rune Graversen <rune@misu.su.se>
Affiliation:	Stockholms universitet
Duration:	2014-07-30 – 2015-08-01
Classification:	10501 10508 10502
Keywords:

Abstract

Background: Although the Arctic summer sea-ice cover shows a clear negative trend over recent decades, the year-to-year variability of the summer ice cover is large. Recent studies have shown that atmospheric processes in spring play an important role for the initiation of the summer ice melt and therefore largely determine the September sea-ice concentration (e.g. Kapsch et al. 2013). In Kapsch et al. (2013) it was concluded that enhanced longwave radiation associated with positive humidity and cloud anomalies during spring plays a significant role in initiating the summer ice melt, and that the shortwave-radiation anomalies act as an amplifying feedback once the melt has started. Description: The main focus is to further study the cause and response relationship between atmospheric spring anomalies and the sea ice. While the previous studies are based on atmospheric reanalysis products, a global climate model (GCM) is used in the present study in order to investigate the aforementioned processes in further depth. We use the Community Climate System Model (CCSM) version 4 (Gent et al., 2011). Using this fully coupled atmosphere-ice-ocean GCM, we can investigate the effect of different atmospheric anomalies on sea ice separately. For instance the effect from cloud anomalies can be studied by implementing anomalies of cloud fields in the model. Such studies are normally not possible based on observational data alone, but need to be performed with models in order to control the different fields and modify them one by one. To our knowledge a decomposition of the effect on sea ice from different atmospheric anomalies of e.g. humidity, clouds, and atmospheric temperatures has not been done before. Further by using the model it can be investigated how the September sea-ice cover is affected by the timing of the atmospheric anomalies. For instance the effect on the sea ice from atmospheric anomalies occurring in spring can be compared to anomalies occurring in the summer season. References: Kapsch, M.-L., R. G. Graversen, and M. Tjernstrom (2013), Springtime atmospheric energy transport and the control of Arctic summer sea-ice extent, Nature Climate Change 3, 744-748, doi:10.1038/NCLIMATE1884. Gent, Peter R., and Coauthors, 2011: The Community Climate System Model Version 4. J. Climate, 24, 4973–4991, doi: 10.1175/2011JCLI4083.1