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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 1
Biogeosciences, 13, 133–145, 2016
https://doi.org/10.5194/bg-13-133-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Catastrophic reduction of sea ice in the Arctic Ocean...

Biogeosciences, 13, 133–145, 2016
https://doi.org/10.5194/bg-13-133-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 15 Jan 2016

Research article | 15 Jan 2016

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

A. Ooki1, S. Kawasaki1, K. Kuma1, S. Nishino2, and T. Kikuchi2 A. Ooki et al.
  • 1Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan
  • 2Institute of Arctic Climate and Environment Research, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan

Abstract. We conducted a shipboard observation over the Chukchi Sea and the Canada Basin in the western Arctic Ocean in September and October 2012 to obtain vertical distributions of four volatile organic iodine compounds (VOIs) in seawater. The VOIs observed in this study were iodomethane (CH3I), iodoethane (C2H5I), diiodomethane (CH2I2), and chloroiodomethane (CH2ClI). Maximum concentrations of the four VOIs were found in the bottom layer water over the Chukchi Sea shelf, in which layer the maximum concentration of ammonium (NH4+) also occurred. A significant correlation was observed between C2H5I and NH4+ (correlation coefficient R = 0.93, P < 0.01, n = 64) and between CH3I and NH4+ (R= 0.77, P < 0.01, n =  64), suggesting that the production of these VOIs increased with the degradation of organic matter. Over the northern Chukchi Sea shelf–slope area, concentration maxima of CHI2, CH2ClI, and CH3I were found in the subsurface cold, dense water (CDW). A large nitrogen deficit (N deficit  =  NH4++ NO3+ NO2−16PO43−) occurred simultaneously in this water, suggesting the production of the three VOIs in the sediment or the bottom layer water over the shelf, probably in association with the degradation of organic matter. We conclude that VOI production over the Chukchi Sea shelf can be largely attributed to the degradation of organic matter that is produced in the highly productive shelf water. High concentrations of CH2ClI were also found in the Alaskan Coastal Water (ACW) from the Bering Strait to the surface of the northern Chukchi slope. The VOIs that originated at the Chukchi Sea shelf are expected to be laterally transported to the Arctic Ocean basin through the CDW and the surface ACW.

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We conducted a shipboard observation over the Chukchi Sea and the Canada Basin in the western Arctic Ocean to obtain vertical distributions of four volatile organic iodine compounds (VOIs) in seawater. High concentrations of four VOIs were found in the bottom layer water over the Chukchi Sea shelf, in which layer the concentration maximum of ammonium occurred simultaneously. We considered that the VOI production is associated with degradation of organic matter in the bottom sediment.
We conducted a shipboard observation over the Chukchi Sea and the Canada Basin in the western...
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