Shelf‐basin exchange times of Arctic surface waters estimated from <sup>228</sup>Th/<sup>228</sup>Ra disequilibrium

Loeff, Michiel Rutgers v. d.; Cai, Pinghe; Stimac, Ingrid; Bauch, Dorothea; Hanfland, Claudia; Roeske, Tobias; Moran, S. Bradley

doi:10.1029/2011jc007478

Cited by 35 publications

(51 citation statements)

References 88 publications

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“…This concept is supported by a Ra/Th estimate of shelf water residence ages of at least 8 years, which is much older than *3 years for waters in the Transpolar Drift over the Lomonosov Ridge [39]. This considerably longer residence time of shelf waters may be a factor for the missing variability in d 13 C DIC in the Eurasian Basin due to a stronger degradation of any shelfsourced biological signal in this region.…”

Section: Biotic and Non-biotic Influences On D 13 C Dic In The Arcticsupporting

confidence: 48%

“…While biological productivity over the Barents Sea and northern Kara seas can be high, the signals of production and remineralization with high and low d 13 C DIC , respectively, are apparently not transported into the Eurasian Basin. This may be connected to a weaker stratification in the Eurasian Basin and sufficient degradation of any shelf-sourced biological signal potentially present in this region as shelf waters recirculating in the Eurasian Basin have a relatively long residence time of at least 8 years [39].…”

Section: Summary and Future Directionsmentioning

confidence: 99%

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A baseline for the vertical distribution of the stable carbon isotopes of dissolved inorganic carbon (δ13CDIC) in the Arctic Ocean

Bauch

Polyak

Ortiz

2015

Arktos

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Stable carbon isotopes of dissolved inorganic carbon (d 13 C DIC ) in the ocean are generally not well understood as they are governed by a complex interplay of biological processes and air-sea exchange. In the Arctic Ocean, d 13 C DIC values are prone to change in the near future with rapidly changing climate conditions. This study provides a baseline to assess the d 13 C DIC of the Arctic Ocean with a focus on upper to intermediate waters (to *500 m). Measured d 13 C DIC values in the Arctic Ocean range from *-0.6 to ?2.2 %. In the Eurasian Basin, the d 13 C DIC values lie between *1 and 1.5 % and exhibit little variation within the upper layers. In the Canada Basin, d 13 C DIC values reach 2 % in the surface layer, with lowest values of *-0.6 % found at *200 m water depth. At greater depth, d 13 C DIC values range from *1 to 1.5 % within both basins. In the Canada Basin, nutrient levels are higher than in the Eurasian Basin and associated variations in d 13 C DIC are clearly related to biological processes. However, low d 13 C DIC values in the Canada Basin are also strongly influenced by non-equilibrium air-sea exchange processes. The different d 13 C DIC patterns between the Canada Basin and the Eurasian Basin appear to be linked to differences in transport processes within the Arctic Ocean halocline. The upper layers in the Canada basins have direct contributions of waters from the Laptev, East Siberian and Chukchi shelves, which contain elevated fractions of river waters and sea-ice related brines, whereas their counterparts, in the Eurasian Basin, are mostly formed by halocline waters from the Barents and Kara seas. River waters have low d 13 C DIC of *-8 % on average, but in the Arctic basins this signal is mostly lost and d 13 C DIC values show only a weak correlation to river water fractions contained in the water mass. No relation between d 13 C DIC and sea-ice related brine contribution is apparent.

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Section: Biotic and Non-biotic Influences On D 13 C Dic In The Arcticsupporting

confidence: 48%

Section: Summary and Future Directionsmentioning

confidence: 99%

A baseline for the vertical distribution of the stable carbon isotopes of dissolved inorganic carbon (δ13CDIC) in the Arctic Ocean

Bauch

Polyak

Ortiz

2015

Arktos

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“…In 2008, residence times for river run‐off over the shelf break in the Laptev Sea and over the Lomonosov Ridge were estimated to be 2.5 ± 0.5 years [ Bauch et al ., ]. Strong and continuous offshore winds can lead to residence times as short as 1 year on the Laptev Sea shelf [ Bauch et al ., ; Rutgers van der Loeff et al ., ]. Short residence times of <1 year were also found for surface waters in the Kara Sea suggesting rapid advection of tDOC from the Ob and Yenisei onto the Laptev Shelf where it mixes with tDOC from the Lena River [ Harms et al ., ].…”

Section: Discussionmentioning

confidence: 99%

The fate of terrigenous dissolved organic carbon on the Eurasian shelves and export to the North Atlantic

2017

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Dissolved lignin phenols, chromophoric dissolved organic matter (CDOM) absorption, and fluorescence were analyzed along cross‐slope mooring locations in the Barents, Laptev, and East Siberian Seas to gain a better understanding of terrigenous dissolved organic carbon (tDOC) dynamics in Arctic shelf seas and the Arctic Ocean. A gradient of river water and tDOC was observed along the continental shelf eastward into the East Siberian Sea. Correlations of carbon‐normalized yields of lignin‐derived phenols supplied by Siberian rivers with river water fractions and known water residence times yielded in situ decay constants of 0.18–0.58 yr−1. Calculations showed ∼50% of annual tDOC discharged by Siberian rivers was mineralized in estuaries and on Eurasian shelves per year indicating extensive removal of tDOC. Bioassay experiments and in situ decay constants indicated a reactivity continuum for tDOC. CDOM parameters and acid/aldehyde ratios of vanillyl (V) and syringyl (S) lignin phenols showed biomineralization was the dominant mechanism for the removal of tDOC. Characteristic ratios of p‐hydroxy (P), S, and V phenols (P/V, S/V) also identified shelf regions in the Kara Sea and regions along the Western Laptev Sea shelf where formation of Low Salinity Halocline Waters (LSHW) and Lower Halocline Water (LHW) occurred. The efficient removal of tDOC demonstrates the importance of Eurasian margins as sinks of tDOC derived from the large Siberian Rivers and confirms tDOC mineralization has a major impact on nutrients budgets, air‐sea CO2 exchange, and acidification in the Siberian Shelf Seas.

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“…The TPD track and relative contributions of the different shelf seas is known to vary with the Arctic Oscillation index (Macdonald et al, 2005). Surface concentrations of DFe inside the TPD are expected to be dictated by a strong riverine influence (Bauch et al, 2011;Klunder et al, 2012a;Roeske et al, 2012;Rutgers van der Loeff et al, 2012;Slagter et al, 2017). One major impact of climate change is the thaw of permafrost soil (Stedmon et al, 2011;Schuur et al, 2015) resulting in an increase in DOM released into the Arctic Ocean (Vonk et al, 2012(Vonk et al, , 2013.…”

Section: Surface and Shelfmentioning

confidence: 99%

Dissolved Fe in the Deep and Upper Arctic Ocean With a Focus on Fe Limitation in the Nansen Basin

et al. 2018

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Shelf‐basin exchange times of Arctic surface waters estimated from ²²⁸Th/²²⁸Ra disequilibrium

Cited by 35 publications

References 88 publications

A baseline for the vertical distribution of the stable carbon isotopes of dissolved inorganic carbon (δ13CDIC) in the Arctic Ocean

A baseline for the vertical distribution of the stable carbon isotopes of dissolved inorganic carbon (δ13CDIC) in the Arctic Ocean

The fate of terrigenous dissolved organic carbon on the Eurasian shelves and export to the North Atlantic

Dissolved Fe in the Deep and Upper Arctic Ocean With a Focus on Fe Limitation in the Nansen Basin

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Shelf‐basin exchange times of Arctic surface waters estimated from 228Th/228Ra disequilibrium

Cited by 35 publications

References 88 publications

A baseline for the vertical distribution of the stable carbon isotopes of dissolved inorganic carbon (δ13CDIC) in the Arctic Ocean

A baseline for the vertical distribution of the stable carbon isotopes of dissolved inorganic carbon (δ13CDIC) in the Arctic Ocean

The fate of terrigenous dissolved organic carbon on the Eurasian shelves and export to the North Atlantic

Dissolved Fe in the Deep and Upper Arctic Ocean With a Focus on Fe Limitation in the Nansen Basin

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Product

Resources

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Shelf‐basin exchange times of Arctic surface waters estimated from ²²⁸Th/²²⁸Ra disequilibrium