Distribution, transport, and production of volatile halocarbons in the upper waters of the ice‐covered high Arctic Ocean

Abstract

[1] Volatile halogenated compounds (CHBr 3 , CH 2 Br 2 , CHBr 2 Cl, and CH 2 ClI) were measured in the water column and in sea ice brine across the Arctic Ocean, from Barrow, Alaska, to Svalbard, during the Beringia 2005 expedition (August-September) with RV/IB Oden. High concentrations of brominated compounds (up to 42 pmol kg À1 of bromoform) were found under multiyear ice in the surface waters over the Makarov Basin and the Lomonosov Ridge, near the North Pole. Even higher concentrations (bromoform up to 160 pmol kg À1 ) were found in sea ice brine. We propose that the high load of riverine dissolved organic matter that is transported in the Transpolar Drift is a main factor responsible for the high concentration of brominated volatile compounds found in sea ice brine and upper waters and that cycles of freezing and thawing during the transport enhance the transfer of halocarbons to the seawater. The iodinated compound (CH 2 ClI) showed a completely different distribution with highest concentrations in water of Pacific origin in the mixed layer and upper halocline of the northern Canada Basin and over the Alpha Ridge. In the southern Canada Basin, low concentrations of halocarbons were found in upper waters. Higher concentrations in water of Pacific origin, especially on the continental shelf, indicate production in the shelf regions, likely in the Chukchi Sea and the East Siberian Sea.

Concentration maxima of volatile organic iodine compounds in the bottom layer water and the cold, dense water over the Chukchi Sea in the western Arctic Ocean: a possibility of production related to degradation of organic matter

“…Previously, NH + 4 concentrations in coastal subarctic seawater have been observed to increase in the bottom layer water (∼ 90 m depth) after the spring bloom of diatoms (Kudo et al, 2007). Therefore, we suggest that the production of C 2 H 5 I and CH 3 I associated with the degradation of organic matter occurs in the bottom layer water, probably after the diatom bloom, over the Chukchi Sea shelf.…”

Concentration maxima of volatile organic iodine compounds in the bottom layer water and the cold, dense water over the Chukchi Sea in the western Arctic Ocean: a possibility of production related to the degradation of organic matter

“…The lateral transport of CH 2 ClI from the Chukchi Sea to the northern Canada Basin in ACW through the mixed layer, and to the Alpha Ridge (85 • N) in the Pacific-origin CDW through the subsurface upper halocline layer has recently been reported by Karlsson et al (2013). The VOIs produced over the Chukchi Sea shelf might have the potential to supply iodine to Arctic air far from the shelf.…”

“…CH 3 I was measured in the Greenland and Norwegian seas (63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73)(74)(75) • N) in November (Happell and Wallace, 1996). CH 2 ClI was measured in the Arctic Ocean basin from Barrow,Alaska, • N; Karlsson et al, 2013). CH 3 I, C 2 H 5 I, CH 2 ClI, and C 3 H 7 I were measured in the Greenland and Norwegian seas (78)(79)(80)(81)(82) • N) in June and July (Atkinson et al, 2014).…”

“…CH 3 I, C 2 H 5 I, CH 2 ClI, and C 3 H 7 I were measured in the Greenland and Norwegian seas (78)(79)(80)(81)(82) • N) in June and July (Atkinson et al, 2014). There have been very few measurements of VOIs in the western (Pacific sector) Arctic Ocean (Karlsson et al, 2013), which has vast continental shelves.…”

Natural and anthropogenic sources of bromoform and dibromomethane in the oceanographic and biogeochemical regime of the subtropical North East Atlantic

“…Here, colder surface temperatures indicate nutrient input, leading to elevated chlorophyll a, which has been observed to coincide with higher CHBr 3 and CH 2 Br 2 concentrations and an elevated ratio of around 4 in this and other biologically active regions. 21,27,39,74,75,77,78 In comparison to the region around the Cape Verde Archipelago, the fresher upwelling and more oxic conditions possibly lead to this higher CHBr 3 to CH 2 Br 2 ratio.…”