Seasonal variability of methyl iodide in the Kiel Fjord. Issue 3 (6th March 2014)

• Record Type: Journal Article
• Authors: Shi, Qiang; Petrick, Gert; Quack, Birgit; Marandino, Christa; Wallace, Douglas
• Is Part Of: Journal of geophysical research. Volume 119:Issue 3(2014:Mar.)
• Page Start: 1609
• Page End: 1620
• Publication Date: 2014-03-06
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2013JC009328
• Languages: English
• ISSNs: 2169-9275

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>From October 2008 to November 2010, CH<sub>3</sub>I concentrations were measured in the Kiel Fjord together with potentially related biogeochemical and physical parameters. A repeating seasonal cycle of CH<sub>3</sub>I was observed with highest concentrations in summer (ca. 8.3 pmol L<sup>−1</sup>; June and July) and lowest concentrations in winter (ca. 1.5 pmol L<sup>−1</sup>; December to February). A strong positive correlation at zero lag between [CH<sub>3</sub>I] and solar radiation (R<sup>2</sup> = 0.93) was observed, whereas correlations with other variables (SST, Chlorophyll <italic>a</italic>) were weaker, and they lagged CH<sub>3</sub>I by ca. 1 month. These results appear consistent with the hypothesis that SSR is the primary forcing of CH<sub>3</sub>I production in surface seawater, possibly through a photochemical pathway. A mass balance of the monthly averaged data was used to infer mean rates of daily net production (P<sub>net</sub>) and losses for CH<sub>3</sub>I over the year. The sea‐to‐air flux of CH<sub>3</sub>I in the Kiel Fjord averaged 3.1 nmol m<sup>−2</sup> d<sup>−1</sup>, the mean chemical loss rate was 0.047 pmol L<sup>−1</sup> d<sup>−1</sup>, and P<sub>net</sub> varied systematically from winter to summer (from 0 to 0.6 pmol L<sup>−1</sup> d<sup>−1</sup>). P<sub>net</sub> was correlated at zero lag with SST, SSR, and Chl<italic>a</italic> (R<sup>2</sup> = 0.55, 0.67, and 0.73, respectively, p << 0.01). The lagged cross‐correlation analysis indicated that SSR led P<sub>net</sub> by 1 month, whereas the strongest cross correlations with Chl<italic>a</italic> were at lags of 0 to +1 month, and SST lagged P<sub>net</sub> by 1 month. The broad seasonal peak of P<sub>net</sub> makes it difficult to determine the key factor controlling CH<sub>3</sub>I net production using in situ concentration data alone.</p> </abstract>