200-YEAR RECORD OF BIOGENIC SULFUR IN A SOUTH GREENLAND ICE CORE (20D)

The concentration of methanesulfonic acid (MSA) was determined in a sh allow south central Greenland ice core (20D). This study provides a hi gh-resolution record of the DMS-derived biogenic sulfur in Greenland p recipitation over the past 200 years. The mean concentration of MSA is 3.30 ppb (sigma=2.38 ppb,n=1134). The general trend of MSA is an incr ease from 3.01 to 4.10 ppb between 1767 and 1900, followed by a steady decrease to 2.34 ppb at the present time. This trend is in marked con trast to that of non-sea-salt sulfate (nss SO42-), Which increases dra matically alter 1900 due to the input of anthropogenic sulfur. The MSA fraction ((MSA/(MSA+nssSO(4)(2-)))100) ranges from a mean of 15% in preindustrial ice to less than 5% in recent ice. These MSA fractions s uggest that approximately 15 to 40% of the sulfur in recent Greenland ice is of biological origin. It is suggested that there is a significa nt low-latitude component to the biogenic sulfur in the core and that variations in the MSA fraction reflect changes in the relative strengt hs of low- and high-latitude inputs. The data show no evidence for a s trong dependence of dimethyl sulfide (DMS) emissions on sea surface te mperature during the last century. There is also no indication that th e yield of MSA from DMS oxidation has been altered by increased NOx le vels over the North Atlantic during this period.