Methane Sulphonic Acid in East Antarctic Coastal Firn and Ice Cores and Its Relationship with Chlorophyll-a and Sea Ice Extent
Abstract. Sea ice is important for both regional and global climate, but comprehensive sea ice records are lacking pre-1978, when global-scale spaceborne observations began. Attempts to reconstruct sea ice conditions in different regions of Antarctica with the help of methane sulphonic acid (MSA) records from ice cores have had varying success, highlighting the often-regional relationship between ice core MSA and sea ice. This study uses MSA records from three firn cores and one ice core drilled on Fimbul Ice Shelf in Dronning Maud Land, East Antarctica, to investigate the relationship to satellite-derived sea ice extent (SIE) in the Southern Ocean. Chlorophyll-a concentrations, serving as a measure of phytoplankton biomass, are correlated to the MSA records to further test the MSA – SIE relationship. The relationship to both SIE and chlorophyll-a differs largely between the different firn and ice core MSA records. We find significant correlations for the MSA records from the two higher accumulation core sites to SIE and chlorophyll-a in the Weddell Sea, Western Pacific Ocean, and Ross Sea Sectors. Furthermore, the use of stacked MSA records introduced significant correlations between MSA from the lower accumulation core sites and SIE. The absence of coherent correlation patterns between the MSA records across the four investigated cores and SIE or chlorophyll-a in the Southern Ocean suggests that the Fimbul Ice Shelf MSA records are not consistent proxies for regional SIE.
Viewed (geographical distribution)