Open ocean DMS air/sea fluxes over the eastern South Pacific Ocean

Abstract

Abstract. Air/sea fluxes of dimethylsulfide (DMS) were measured by eddy correlation over the Eastern South Pacific Ocean during January 2006. The cruise track extended from Manzanillo, Mexico, along 110 • W, to Punta Arenas, Chile. Bulk air and surface ocean DMS levels were also measured and gas transfer coefficients (k DMS ) were computed. Air and seawater DMS measurements were made using chemical ionization mass spectrometry (API-CIMS) and a gas/liquid membrane equilibrator. Mean surface seawater DMS concentrations were 3.8±2.2 nM and atmospheric mixing ratios were 340±370 ppt. The air/sea flux of DMS was uniformly out of the ocean, with an average value of 12±15 µmol m −2 d −1 . Sea surface concentration and flux were highest around 15 • S, in a region influenced by shelf waters and lowest around 25 • S, in low chlorophyll gyre waters. The DMS gas transfer coefficient exhibited a linear wind speed-dependence over the wind speed range of 1 to 9 m s −1 . This relationship is compared with previously measured estimates of k from DMS, CO 2 , and dual tracer data from the Atlantic and Pacific Ocean, and with the NOAA/COARE gas transfer model. The model generated slope of k vs. wind speed is at the low end of those observed in previous DMS field studies.

High-resolution measurements of elemental mercury in surface water for an improved quantitative understanding of the Baltic Sea as a source of atmospheric mercury

“…The strongest impact on the results was most likely the differences in the k parameterizations that had been applied. These included the k(u) of Liss and Merlivat (1986) (LM86), Nightingale et al (2000) (Night2000), and Wanninkhof (1992) that was used in the form k 660 = 0.31u 2 or k 660 = 0.39u 2 (WH92) according to the type of wind speed data, as well as a parameterization determined in the Baltic Sea (Weiss et al, 2007), Weiss2007. Since k(u) consists of two parts (Eq.…”

“…The approved bottle equilibrator first implemented in 2006 was then used for validation. A membrane equilibrator was already successfully applied for the measurements of dimethyl sulfide in seawater (Marandino et al, 2009). In our study seawater was supplied either from the sea surface, pumped from below the ship's hull (R/V Elisabeth Mann Borgese) or from the bow of the ship (R/V Meteor) at ∼ 3-4 m depth, or from a depth down to ∼ 300 m, pumped by the pump-CTD.…”

“…The exchange of many gases and gaseous compounds has been studied using the film model (Broecker and Peng, 1974;Liss, 1973;Liss and Merlivat, 1986). The property of elemental mercury (Hg 0 ) that allows it to be subjected to seaair gas exchange is unique among heavy metals.…”

“…The latter is determined by the atmospheric equilibration of the gas, depending on its solubility. The gas exchange transfer velocity has mainly been studied for carbon dioxide and is used as a standard for freshwater and seawater at 20 • C (Liss and Merlivat, 1986;Nightingale et al, 2000;Wanninkhof, 1992). Ionic mercury in seawater originates from anthropogenic emissions but also from natural sources, such as weathering and geogenic activity.…”

High-resolution measurements of elemental mercury in surface water for an improved quantitative understanding of the Baltic Sea as a source of atmospheric mercury

“…The approved bottle equilibrator first implemented in 2006 was then used for validation. A membrane equilibrator was already successfully applied to the measurements of dimethylsulfide in seawater (Marandino et al, 2009). In our study seawater was supplied either from the sea surface, pumped from below the ship's hull (r/v Elisabeth Mann Borgese) or from the bow of 20 the ship (r/v Meteor) at ~3-4 m depth, or from a depth down to ~300 m, pumped by the pump-CTD.…”