25th International Meeting on Organic Geochemistry IMOG 2011

P-234
Constraining the sources of dissolved and particulate organic
carbon to the Arctic Ocean using full-depth dual carbon isotope
profiles of DIC, DOC, and POC
David Griffith 1 , Ann McNichol 2 , Li Xu 2 , Timothy Eglinton 3 , Fiona McLaughlin 4 , Robie
Macdonald 4 , Kristina Brown 5
1 MIT/WHOI Joint Program in Oceanography, Woods Hole, MA, United States of America, 2 NOSAMS,
Woods Hole Oceanographic Institution, Woods Hole, MA, United States of America, 3 Dept. of Chemistry and
Marine Geochemistry, WHOI, Woods Hole, MA, United States of America, 4 Institute of Ocean Sciences,
Fisheries and Oceans Canada, Sidney, BC, Canada, 5 University of British Columbia, Vancouver, BC,
Canada (corresponding author:dgriffith@whoi.edu)
The ability to predict how the Arctic Ocean will
respond to a changing climate is hindered by our
limited understanding of the factors that control
organic carbon (OC) dynamics in this unique system.
Dual carbon isotope ( 13 C and 14 C) measurements are
a powerful tool for characterizing ocean water masses
and studying carbon cycling in a variety of marine
environments. As such, isotopic measurements
represent a great opportunity to improve our
understanding of the Arctic Ocean carbon cycle and
set a baseline for monitoring biogeochemical changes
that may occur in the coming decades. Yet there exist
only a few full-depth ocean profiles of coupled 13 C and
14 C measurements of dissolved and particulate OC
(DOC and POC), and none have been reported for
the Arctic Ocean. In this study we present full-depth,
dual isotope profiles of dissolved inorganic carbon
(DIC), DOC, and suspended POC at two sites in the
Canada Basin with different seasonal ice coverage
characteristics.
Our results are consistent with the dominant water
masses of the area, and point to the importance of
river discharge, sea-ice algae, OC sorption, lateral
particle transport, and the potential for
chemoautotrophic production. Although the two sites
have similar DI 13 C and DI 14 C profiles, the seasonally
ice-free site (CB4) has a depleted (older) 14 C
signature in the DOC, suspended POC, and sinking
POC pools compared to the perennially ice-covered
site (CB9). And unlike other ocean basins, suspended
POC in the Canada Basin is significantly younger
than sinking POC throughout the water column, which
raises questions as to the source of suspended POC
in the mesopelagic Arctic Ocean.
Figure 1. Profiles of � 14 C at a seasonally ice-free
station (CB4) in the Canada Basin.
371