Inventories and behavior of particulate organic carbon in the Laptev and East Siberian Seas
L. Sánchez-García, V. Alling, S. Pugach, J. Vonk, B. van Dongen, C. Humborg, O. Dudarev, I. Semiletov, Ö. Gustafsson. Inventories and behavior of particulate organic carbon in the Laptev and East Siberian Seas. Global Biogeochemical Cycles. 2011, Vol. 25, p. GB2007, 13 PP.-2011.
Fluvial and erosional release processes in permafrost‐dominated Eurasian Arctic cause
transport of large amounts of particulate organic carbon (POC) to coastal waters. The
marine fate of this terrestrial POC (terr‐POC), water column degradation, burial in shelf
sediments, or export to depth, impacts the potential for climate‐carbon feedback. As part of
the International Siberian Shelf Study (ISSS‐08; August–September 2008), the POC
distribution, inventory, and fate in the water column of the extensive yet poorly studied
Eurasian Arctic Shelf seas were investigated. The POC concentration spanned 1–152 mM,
with highest values in the SE Laptev Sea. The POC inventory was constrained for the
Laptev (1.32 ± 0.09 Tg) and East Siberian seas (2.85 ± 0.20 Tg). A hydraulic residence
time of 3.5 ± 2 years for these Siberian shelf seas yielded a combined annual terr‐POC
removal flux of 3.9 ± 1.4 Tg yr−1. Accounting for sediment burial and shelf‐break
exchange, the terr‐POC water column degradation was ∼2.5 ± 1.6 Tg yr−1, corresponding
to a first‐order terr‐POC degradation rate constant of 1.4 ± 0.9 yr−1, which is 5–10 times
faster than reported for terr‐DOC degradation in the Arctic Ocean. This terr‐POC
degradation flux thus contributes substantially to the dissolved inorganic carbon excess
of 10 Tg C observed during ISSS‐08 for these waters. This evaluation suggests that
extensive decay of terr‐POC occurs already in the water column and contributes to
outgassing of CO2. This process should be considered as a geographically dislocated
carbon‐climate coupling where thawing of vulnerable permafrost carbon on land is
eventually adding CO2 above the ocean.
Fluvial and erosional release processes in permafrost‐dominated Eurasian Arctic cause
transport of large amounts of particulate organic carbon (POC) to coastal waters. The
marine fate of this terrestrial POC (terr‐POC), water column degradation, burial in shelf
sediments, or export to depth, impacts the potential for climate‐carbon feedback. As part of
the International Siberian Shelf Study (ISSS‐08; August–September 2008), the POC
distribution, inventory, and fate in the water column of the extensive yet poorly studied
Eurasian Arctic Shelf seas were investigated. The POC concentration spanned 1–152 mM,
with highest values in the SE Laptev Sea. The POC inventory was constrained for the
Laptev (1.32 ± 0.09 Tg) and East Siberian seas (2.85 ± 0.20 Tg). A hydraulic residence
time of 3.5 ± 2 years for these Siberian shelf seas yielded a combined annual terr‐POC
removal flux of 3.9 ± 1.4 Tg yr−1. Accounting for sediment burial and shelf‐break
exchange, the terr‐POC water column degradation was ∼2.5 ± 1.6 Tg yr−1, corresponding
to a first‐order terr‐POC degradation rate constant of 1.4 ± 0.9 yr−1, which is 5–10 times
faster than reported for terr‐DOC degradation in the Arctic Ocean. This terr‐POC
degradation flux thus contributes substantially to the dissolved inorganic carbon excess
of 10 Tg C observed during ISSS‐08 for these waters. This evaluation suggests that
extensive decay of terr‐POC occurs already in the water column and contributes to
outgassing of CO2. This process should be considered as a geographically dislocated
carbon‐climate coupling where thawing of vulnerable permafrost carbon on land is
eventually adding CO2 above the ocean.