NonConservative Behavior of Terrigenous Dissolved Organic Carbon in the Western Arctic Ocean

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Non-Conservative Behavior of Terrigenous
Dissolved Organic Carbon in the Western Arctic
Ocean

• Dennis Hansell
• Dave Kadko
• Nick Bates
• RSMAS, Univ. of Miami
• Bermuda Biological Station for Research, Inc.

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Arctic River Discharges (11 of global discharge
is into the Arctic Ocean)
(mean annual discharges in km3)
http//www.awi-bremerhaven.de/Modelling/ARCTIC/pro
jects/rivers/rivers.html
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Arctic winter surface salinity
Salinity
From http//psc.apl.washington.edu/
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Conservative Mixing of Terrigenous DOC in the
Ocean (0.25 Pg C yr-1 globally)
Net addition of DOC
Net loss of DOC
Note Intercept
Data from Amon and Benner 2003
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Conservative Mixing of Terrigenous DOC in the
Ocean (0.25 Pg C yr -1 globally)
Change in Intercept
Data from Amon and Benner 2003
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DOC (color) and Salinity (lines) in Spring 2002
Polar Mixed Layer low salinity mix of Pacific
and river waters high DOC
Pacific water
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DOC vs Salinity in Western Arctic
y -2.596x 154.5 R2 0.39
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Eurasian Arctic
Western Arctic
y -2.596x 154.5 R2 0.39
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Differences in circulation of Eurasian and Canada
sides
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228Ra/226Ra - A tracer of time since water left
the shelf
T1/2 5.78 y
T1/2 1010 y
232Th (in sediments)
228Th (in water column)
228Ra (in water column)
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228Ra/226Ra in the Transpolar Drift (Rutgers van
der Loeff et al 1995)
Young, low salinity water from the shelf
TPD lt3 years
Old Atlantic water
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T3
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228Ra/226Ra in the Trans Polar Drift and at Ice
Station T3 in the Beaufort Gyre (Kaufman et al.
1973)
TPD lt3 years
20 years
T3
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Locations of 228Ra/226Ra measurements during the
Shelf-basin Interaction (SBI) Project
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228Ra/226Ra an index of the time since the
water was over the shelves
Transpolar drift (Eurasian) (short residence time)
Beaufort Gyre (Long residence time)
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Transpolar Drift ( ), Ice Station T3 ( ), SBI
area (O)
young Pacific water
aged Beaufort Gyre water
old Atlantic water
How old is the water in the SBI area?
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228Ra/226Ra ratio and apparent age on a transect
across the Chukchi Sea shelf break
Modeled Age
Zero-Age Ratio
Modeled Age (y)
228Ra/226Ra
Measured Ratio
Off Shelf
On Shelf
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Finding Removal of Terrigenous DOC in the
western Arctic Ocean

• Age of gyre water in the SBI region 13 years
• 300-400 microM tDOC removed over this time period
• Half life of tDOC is 7.1 years
• Decay constant of tDOC is 0.093 yr-1