Dimethylated sulfur compounds in the Peruvian upwelling system

[摘要] Our understanding of the biogeochemical cycling of theclimate-relevant trace gas dimethyl sulfide (DMS) in the Peruvian upwellingsystem is still limited. Here we present oceanic and atmospheric DMSmeasurements which were made during two shipborne cruises in December 2012(M91) and October 2015 (SO243) in the Peruvian upwelling region.Dimethylsulfoniopropionate (DMSP) and dimethyl sulfoxide (DMSO) were alsomeasured during M91. DMS concentrations were 1.9  ±  0.9 and 2.5  ±  1.9 nmol L −1 in surface waters in October 2015 andDecember 2012, respectively. Nutrient availability appeared to be the maindriver of the observed variability in the surface DMS distributions in thecoastal areas. DMS, DMSP, and DMSO showed maxima in the surface layer, and noelevated concentrations associated with the oxygen minimum zone off Peruwere measured. The possible role of DMS, DMSP, and DMSO as radical scavengers(stimulated by nitrogen limitation) is supported by their negativecorrelations with N:P (sum of nitrate and nitrite : dissolved phosphate)ratios. Large variations in atmospheric DMS mole fractions were measuredduring M91 (144.6  ±  95.0 ppt) and SO243 (91.4  ±  55.8 ppt);however, the atmospheric mole fractions were generally low, and thesea-to-air flux was primarily driven by seawater DMS. The Peruvian upwellingregion was identified as a source of atmospheric DMS in December 2012 andOctober 2015. However, in comparison to the previous measurements in theadjacent regions, the Peru upwelling was a moderate source of DMS emissions ateither time (M91: 5.9  ±  5.3  µ mol m −2  d −1 ; SO243: 3.8  ±  2.7  µ mol m −2  d −1 ).

[学科分类] 大气科学