228Ra as a tracer for shelf water in the arctic ocean

Loeff, Michiel M. Rutgers van der; Key, Robert M.; Scholten, Jan; Bauch, Dorothea; Michel, A.

doi:10.1016/0967-0645(95)00053-4

Cited by 75 publications

(71 citation statements)

References 34 publications

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“…The distribution can be described as originating from a mixed Siberian continental shelf and river signal entering the Transpolar Drift, in complete agreement with the Radium data from the central Arctic basin (Rutgers van der Loeff et al, 1995). As 226 Ra is practically constant at high salinities, the 228 Ra/ 226 Ra activity ratio can be used instead of 228 Ra, reducing the analytical error.…”

Section: The Possible Applications Of 228 Ra As Tracer In the Arctic supporting

confidence: 70%

“…Here all 228 Ra data can be rather well described by a single conservative mixing line between an ocean component with an AR around 0.15 in the Atlantic Inflow (Rutgers van der Loeff et al, 1995) and a low-salinity (shelf edge) component characterised by station P31 with a AR of 3.9 at a river water percentage of 20% (Figs. 2 and 3).…”

Section: The Estuarine Behaviour Of 228 Ramentioning

confidence: 70%

“…Ostlund and Hut (1984) using the end-member compositions as given by Bauch (1994 1998; Ekwurzel et al, 2001 Loeff et al, 1995) and a low-salinity end-member with a source of 228 Ra and correspondingly high AR. In the southern and eastern Kara Sea and in the Vilkitsky Strait, the sea strait between Kara Sea and Laptev Sea, the AR values are also correlated with salinity, but at an approximately 50% reduced level.…”

Section: Methodsmentioning

confidence: 99%

“…On the sea side, 228 Ra in surface waters closely follows the distribution of river water. In deeper water layers, sources on the slope may also contribute to the 228 Ra signal (Rutgers van der Loeff et al, 1995).…”

Section: The Estuarine Behaviour Of 228 Ramentioning

confidence: 99%

“…As a consequence of parent distribution and of half life, the oceanographic distribution of 226 Ra (1600 years half-life) is primarily controlled by release from deep-sea sediments (Broecker et al, 1967), whereas the distribution of 228 Ra (5.8 years half-life) is characterized by the high activities that can be reached in the shallow water column over wide continental shelf areas (Moore, 1981;Key et al, 1985). 228 Ra is therefore used as a tracer for continental shelf influence in the open ocean (Moore et al, 1986(Moore et al, , 1995Moore, 1987;Li et al, 1980;Rutgers van der Loeff, 1994;Rutgers van der Loeff et al, 1995;Ku et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

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228Ra and 226Ra in the Kara and Laptev seas

Loeff

Kühne

Wahsner

et al. 2003

Continental Shelf Research

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The surface water in the Transpolar Drift in the Arctic Ocean has a strong signature of 228 Ra. In an earlier study of 228 Ra in the open Arctic we showed that the major 228 Ra source had to be in the Siberian shelf seas, but only a single shelf station was published so far. Here we investigate the sources of this signal on the Siberian shelves by measurements of 228 Ra and 226 Ra in surface waters of the Kara and Laptev Sea, including the Ob, Yenisey and Lena estuaries.In the Ob and Lena rivers we found an indication for a very strong and unexpected removal of both isotopes in the early stage of estuarine mixing, presumably related to flocculation of organic-rich material. Whereas 226 Ra behaves conservatively on the shelf, the distribution of 228 Ra is governed by large inputs on the shelves, although sources are highly variable. In the Kara Sea the maximum activity was found in the Baydaratskaya Bay, where tidal resonance and low freshwater supply favour 228 Ra accumulation. The Laptev Sea is a stronger source for 228 Ra than the Kara Sea. Since a large part of Kara Sea water flows through the Laptev Sea, the 228 Ra signal in the Transpolar Drift can be described as originating on the Laptev shelf.The combined freshwater inputs from the Eurasian shelves thus produce a common radium signature with a 228 Ra/ 226 Ra activity ratio of 4.0 at 20% river water. The radium signals of the individual Siberian rivers and shelves cannot be separated, but their signal is significantly different from the signal produced on the Canadian shelf (Smith et al., in press). In this respect, the radium tracers add to the information given by Barium. Moreover, with the 5.8 year half-life of 228 Ra, they have the potential to serve as a tracer for the age of a water mass since its contact with the shelves. r

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Section: The Possible Applications Of 228 Ra As Tracer In the Arctic supporting

confidence: 70%

Section: The Estuarine Behaviour Of 228 Ramentioning

confidence: 70%

Section: Methodsmentioning

confidence: 99%

Section: The Estuarine Behaviour Of 228 Ramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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228Ra and 226Ra in the Kara and Laptev seas

Loeff

Kühne

Wahsner

et al. 2003

Continental Shelf Research

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Size characteristics of chromophoric dissolved organic matter in the Chukchi Sea

et al. 2016

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With the Arctic warming, terrestrial input plays a more important role in carbon cycle in the Arctic Ocean than before. Chromophoric dissolved organic matter (CDOM) as a tracer of terrestrial dissolved organic matter (tDOM) becomes more valuable in elucidating the source and compositions of DOM. Although measurements of DOM in the Arctic Ocean have been widely reported, characteristics of high molecular weight colloids are still poorly understood. In this study, the bulk absorbance and size fractograms of CDOM were measured in the Chukchi Seas using an asymmetrical flow field‐flow fractionation (AF4) coupled online with UV‐vis detectors. Both CDOM a254, absorption coefficient at 254 nm, and the integrated UV254 (from AF4 UV‐vis detector) of three colloidal fractions (1–10, 10–100, and >100 kDa) significantly correlated with the fraction of meteoric water (fmw) calculated from δ18O in seawater, which indicates that the CDOM was mainly derived from terrestrial input and a254 is a potential tracer of tDOM in the Chukchi Sea. Compared with the larger colloidal fractions (10–100 and >100 kDa), the smaller colloidal fraction (1–10 kDa) showed a stronger correlation with the fmw, suggesting the smaller colloids were of mostly terrigenous origin. Values of field measured spectral slope at 275–295 nm (s275–295), a tDOM proxy, were significantly lower than the model‐estimated s275–295 calculated from the MODIS Aqu satellite remote sensing data, which indicated that terrestrial input of CDOM derived from model calculation was likely underestimated in the Chukchi Sea.

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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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228Ra as a tracer for shelf water in the arctic ocean

Cited by 75 publications

References 34 publications

228Ra and 226Ra in the Kara and Laptev seas

228Ra and 226Ra in the Kara and Laptev seas

Size characteristics of chromophoric dissolved organic matter in the Chukchi Sea

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

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