Open AccessStable isotope composition of dissolved inorganic carbon and particulate organic carbon in sea ice from the Ross Sea, Antarctica
Author(s) -
Munro David R.,
Dunbar Robert B.,
Mucciarone David A.,
Arrigo Kevin R.,
Long Matthew C.
Publication year - 2010
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jc005661
Subject(s) - sea ice , salinity , seawater , particulates , oceanography , dissolved organic carbon , total inorganic carbon , total organic carbon , brine , organic matter , environmental chemistry , geology , environmental science , carbon dioxide , chemistry , organic chemistry
We examined controls on the carbon isotopic composition of sea ice brines and organic matter during cruises to the Ross Sea, Antarctica in November/December 1998 and November/December 2006. Brine samples were analyzed for salinity, nutrients, total dissolved inorganic carbon (ΣCO 2 ), and the 13 C/ 12 C ratio of ΣCO 2 Particulate organic matter from sea ice cores was analyzed for percent particulate organic carbon (POC), percent total particulate nitrogen (TPN), and stable carbon isotopic composition ( δ 13 C POC ). ΣCO 2 in sea ice brines ranged from 1368 to 7149 μ mol kg −1 , equivalent to 1483 to 2519 μ mol kg −1 when normalized to 34.5 psu salinity (sΣCO 2 ), the average salinity of Ross Sea surface waters. Sea ice primary producers removed up to 34% of the available ΣCO 2 , an amount much higher than the maximum removal observed in sea ice free water. Carbonate precipitation and CO 2 degassing may reduce sΣCO 2 by a similar amount (e.g., 30%) in the most hypersaline sea ice environments, although brine volumes are low in very cold ice that supports these brines. Brine ranged from −2.6 to +8.0‰ while δ 13 C POC ranged from −30.5 to −9.2‰. Isotopic enrichment of the ΣCO 2 pool via net community production accounts for some but not all carbon isotopic enrichment of sea ice POC. Comparisons of sΣCO 2 , and δ 13 C POC within sea ice suggest that ε p (the net photosynthetic fractionation factor) for sea ice algae is ∼8‰ smaller than the ε p observed for phytoplankton in open water regions of the Ross Sea. These results have implications for modeling of carbon uptake and transformation in the ice‐covered ocean and for reconstruction of past sea ice extent based on stable isotopic composition of organic matter in sediment cores.