Geography

The potential role of sea ice melt in the distribution of chromophoric dissolved organic matter in the Chukchi and Beaufort Seas

Document Type

Article

Abstract

We investigated chromophoric dissolved organic matter (CDOM) in sea ice and the underlying water column in the Chukchi and Beaufort seas of the Pacific Arctic region and its relationship with both physical and biogeochemical parameters. Sea ice, water and melt pond samples were collected as sea ice melted in June–July 2010 and 2011. CDOM absorption was found to be significantly lower in sea ice compared to under-ice waters. In particular, the average CDOM absorption coefficient at 254 nm was approximately four times greater in the underlying water column than in the overlying ice. This indicates that melting sea ice did not contribute to net CDOM at this point in the melt season, but rather diluted CDOM in the under-ice water column. In the 2011 under-ice water column samples, the average CDOM absorption coefficients at 440 nm were twice as high along a transect associated with high phytoplankton biomass, which may have been contributed through subsequent microbial generation of CDOM. Less extensive sea ice cover with melt ponds may also have increased the presence of CDOM owing to increases in light transmission, leading to under-ice phytoplankton blooms and associated microbial production. However, oxygen isotope analysis of these waters with high under-ice phytoplankton biomass also indicates the presence of prior sea ice melt, including potentially sea ice algae and microbes, which could have also contributed to this anomalously high CDOM. These observations suggest that while melting sea ice may not necessarily contribute to increased CDOM concentrations, there are circumstances where CDOM in underlying waters may be higher than expected, either due to enhanced light transmission and higher under-ice production, and/or prior ice melt that provided significant contributions to under-ice CDOM.

Publication Title

Deep-Sea Research Part II: Topical Studies in Oceanography

Publication Date

8-2016

Volume

130

First Page

28

Last Page

42

ISSN

0967-0645

DOI

10.1016/j.dsr2.2016.04.017

Keywords

arctic, biogeochemistry, chromophoric dissolved organic matter (CDOM), dissolved organic matter (DOM), sea ice

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