Seasonal discharge of estuarine freshwater to the western Chukchi Sea shelf identified in stable isotope profiles of mollusk shells

Khim, Boo‐Keun; Krantz, David E.; Cooper, Lee W.; Grebmeier, Jacqueline M.

doi:10.1029/2003jc001816

Cited by 40 publications

(45 citation statements)

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“…The low freshwater endmember value reflects a contribution of halocline waters imported from the Arctic (Alkire, 2010). composition for all the species studied here (e.g., Wassenaar et al, 1988;Khim, 2002;Khim et al, 2003 Although this relationship was originally derived for sponges, it has been successfully applied to hydrographic reconstructions for Arctic regions using data obtained from shells of A. borealis, S. groenlandicus, and Macoma calcarea from Holocene to modern times (Müller-Lupp et al, 2004;Simstich et al, 2005). On the basis of the strong correlation between the δ 18 o water and salinity shown in Figure 3, we rewrite the above equation as:…”

Section: Bivalve Datamentioning

confidence: 99%

“…The use of isotopic data from their shells is gaining significant attention as a valuable tool to generate a much-needed retrospective time series of hydrographic data (Khim et al, 2001(Khim et al, , 2003Müller-Lupp et al, 2003Dettman et al, 2004;Simstich et al, 2005). These organisms accrete calcium carbonate at the ventral margin of their shells throughout the growing period, and this accretion is accentuated in the spring and summer.…”

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confidence: 99%

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Hydrographic Changes in Nares Strait (Canadian Arctic Archipelago) in Recent Decades Based on δ18O Profiles of Bivalve Shells

Torres¹,

Zima²,

Falkner³

et al. 2011

ARCTIC

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ABSTRACT. Nares Strait is one of three main passages of the Canadian Archipelago that channel relatively fresh seawater from the Arctic Ocean through Baffin Bay to the Labrador Sea. Oxygen isotopic profiles along the growth axis of bivalve shells, collected live over the 5 -30 m depth range from the Greenland and Ellesmere Island sides of the strait, were used to reconstruct changes in the hydrography of the region over the past century. The variability in oxygen isotope ratios is mainly attributed to variations in salinity and suggests that the northern end of Nares Strait has been experiencing an increase in freshwater runoff since the mid 1980s. The recent changes are most pronounced at the northern end of the strait and diminish toward the south, a pattern consistent with proximity to the apparently freshening Arctic Ocean source in the north and mixing with Baffin Bay waters as the water progresses southward. This increasing freshwater signal may reflect changes in circulation and ice formation that favor an increased flow of relatively fresh waters from the Arctic Ocean into Nares Strait.

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Section: Bivalve Datamentioning

confidence: 99%

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confidence: 99%

Hydrographic Changes in Nares Strait (Canadian Arctic Archipelago) in Recent Decades Based on δ18O Profiles of Bivalve Shells

Torres¹,

Zima²,

Falkner³

et al. 2011

ARCTIC

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“…The latter was suggested to be inflow from the Pacific Ocean through the Bering Strait, based on the high nutrient concentrations, specifically phosphate. Khim et al (2003) used δ 18 O and δ 13 C to deduce the distribution of freshwater in the water column and terrestrial OM in the sediment. They concluded that the runoff signal could be traced more than 50 km off shore even in the end of summer, about 2 month after the peak river discharge.…”

Section: Introductionmentioning

confidence: 99%

East Siberian Sea, an Arctic region of very high biogeochemical activity

et al. 2011

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Abstract. Shelf seas are among the most active biogeochemical marine environments and the East Siberian Sea is a prime example. This sea is supplied by seawater from both the Atlantic and Pacific Oceans and has a substantial input of river runoff. All of these waters contribute chemical constituents, dissolved and particulate, but of different signatures. Sea ice formation during the winter season and melting in the summer has a major impact on physical as well as biogeochemical conditions. The internal circulation and water mass distribution is significantly influenced by the atmospheric pressure field. The western region is dominated by input of river runoff from the Laptev Sea and an extensive input of terrestrial organic matter. The microbial decay of this organic matter produces carbon dioxide (CO 2 ) that oversaturates all waters from the surface to bottom relative to atmospheric level, even when primary production, inferred from low surface water nutrients, has occurred. The eastern surface waters were under-saturated with respect to CO 2 illustrating the dominance of marine primary production. The drawdown of dissolved inorganic carbon equals a primary production of ∼0.8 ± 2 mol C m −2 , which when multiplied by half the area of the East Siberian Sea, ∼500 000 km 2 , results in an annual primary production of 0.4 (± 1) × 10 12 mol C or ∼4 (± 10) × 10 12 gC. Microbial decay occurs through much of the water column, but dominates at the sediment interface where the majority of organic matter ends up, thus more of the decay products are recycled to the bottom water. High nutrient concentrations and fugacity of CO 2 and low oxygen and pH were observed in the bottom waters. Another signature of organic matter decomposition, methane (CH 4 ), wasCorrespondence to: L. G. Anderson (leifand@chem.gu.se) observed in very high but variable concentrations. This is due to its seabed sources of glacial origin or modern production from ancient organic matter, becoming available due to sub-sea permafrost thaw and formation of so-called taliks. The decay of organic matter to CO 2 as well as oxidation of CH 4 to CO 2 contribute to a natural ocean acidification making the saturation state of calcium carbonate low, resulting in under-saturation of all the bottom waters with respect to aragonite and large areas of under-saturation down to 50 % with respect to calcite. Hence, conditions for calcifying organisms are very unfavorable.

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“…By improving our understanding of processes, time-series data from a shore-based observatory could have the added advantage of providing insight into shortterm observations made elsewhere in the Arctic. For example, a detailed oxygen isotope composition record for the water column could be used throughout the ice-growing season to provide a basis for understanding the annual variability in the oxygen isotope composition of bicarbonate in bivalves that record isotope ratios (e.g., Khim et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

The Potential for Using Little Diomede Island as a Platform for Observing Environmental Conditions in Bering Strait

Cooper¹,

Codispoti²,

Kelly³

et al. 2009

ARCTIC

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ABSTRACT. The Pacific waters that enter the Arctic via the Bering Strait exert a major influence on the Arctic Ocean's stratification, ice cover, and ecosystem. We demonstrate the potential of a shore-based laboratory to monitor the water masses that flow predominantly northward past Little Diomede Island in the center of the Bering Strait into the Arctic Ocean. We determined near-surface water column salinity, inorganic nutrient concentrations, natural fluorescence associated with chlorophyll, and the oxygen isotope composition of seawater, both in summer during the open-water period and in late winter under ice-covered conditions, by pumping ashore water from shallow depths near the island. Additional surveys were undertaken within 5 km of the island to assess the influence of local sources of nutrients. Water mass variability was much greater during the open-water period than under ice-covered conditions, presumably because the relatively immobile ice cover attenuates wind forcing and the decrease in run-off reduces cross-shelf gradients. The mean oxygen isotope composition of the summer (δ 18 O = -1.11‰) and late winter (δ 18 O = -0.98) collections, however, was close to that which has been established for Bering Sea waters in the Pacific-dominated upper halocline of the Arctic Ocean (-1.1‰) particularly considering the higher seasonal flow of runoff in the summer. A comparison with data from shipboard sampling at various locations across the Bering Strait indicates that the oxygen isotope composition of near-surface water sampled at Diomede varies in response to wind-forcing. If the least saline (< 30.5) water near the Alaska coast is excluded, the δ 18O values of Diomede and shipboard samples cannot be distinguished statistically. This similarity suggests that the water sampled from the island also reasonably represents the δ 18O value of Bering Sea waters that contribute to the upper halocline of the Arctic Ocean. Effects of benthic recycling, human activity, and seabird nesting on nutrient concentrations appeared to be concentrated within ~200 m of the island. Our results are discussed in the practical context of availability of electricity, interested local residents, and a geotechnical study indicating that it is feasible to construct and operate a more permanent undersea water intake system to improve environmental observation capabilities in the Bering Strait region.

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Seasonal discharge of estuarine freshwater to the western Chukchi Sea shelf identified in stable isotope profiles of mollusk shells

Cited by 40 publications

References 31 publications

Hydrographic Changes in Nares Strait (Canadian Arctic Archipelago) in Recent Decades Based on δ18O Profiles of Bivalve Shells

Hydrographic Changes in Nares Strait (Canadian Arctic Archipelago) in Recent Decades Based on δ18O Profiles of Bivalve Shells

East Siberian Sea, an Arctic region of very high biogeochemical activity

The Potential for Using Little Diomede Island as a Platform for Observing Environmental Conditions in Bering Strait

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