Discovery and characterization of submarine groundwater discharge in the Siberian Arctic seas: a case study in the Buor-Khaya Gulf, Laptev Sea

It has been suggested that increasing terrestrial water discharge to the Arctic Ocean may partly occur as submarine groundwater discharge (SGD), yet there are no direct observations of this phenomenon in the Arctic shelf seas. This study tests the hypothesis that SGD does exist in the Siberian Arcti...

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Bibliographic Details
Published in:	The cryosphere Vol. 11; no. 5; pp. 2305 - 2327
Main Authors:	Charkin, Alexander N, Michiel Rutgers van der Loeff, Shakhova, Natalia E, Gustafsson, Örjan, Dudarev, Oleg V, Cherepnev, Maxim S, Salyuk, Anatoly N, Koshurnikov, Andrey V, Spivak, Eduard A, Gunar, Alexey Y, Ruban, Alexey S, Semiletov, Igor P
Format:	Journal Article
Language:	English
Published:	Katlenburg-Lindau Copernicus GmbH 05-10-2017 Copernicus Publications
Subjects:	Bottom sediments Brines Carbon dioxide Dissolved organic carbon Drilling Freshwater Geochemistry Geocryology Geoelectricity Geological surveys Groundwater Groundwater discharge Hydrologic cycle Hydrologic models Hydrologic surveys Hydrology Inland water environment Mass balance Nutrients Ocean circulation Organic carbon Permafrost Polar environments Radium 226 Radium isotopes Radium radioisotopes Rivers Saline water Salinity Salinity effects Salts Sediments Shelf seas Stream flow Surface water Surveys Terrestrial environments Transport Water balance Water discharge Water masses Watersheds Winter Arctic Ocean Laptev Sea Lena River Arctic region Yukon River
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Summary:	It has been suggested that increasing terrestrial water discharge to the Arctic Ocean may partly occur as submarine groundwater discharge (SGD), yet there are no direct observations of this phenomenon in the Arctic shelf seas. This study tests the hypothesis that SGD does exist in the Siberian Arctic Shelf seas, but its dynamics may be largely controlled by complicated geocryological conditions such as permafrost. The field-observational approach in the southeastern Laptev Sea used a combination of hydrological (temperature, salinity), geological (bottom sediment drilling, geoelectric surveys), and geochemical (224Ra, 223Ra, 228Ra, and 226Ra) techniques. Active SGD was documented in the vicinity of the Lena River delta with two different operational modes. In the first system, groundwater discharges through tectonogenic permafrost talik zones was registered in both winter and summer. The second SGD mechanism was cryogenic squeezing out of brine and water-soluble salts detected on the periphery of ice hummocks in the winter. The proposed mechanisms of groundwater transport and discharge in the Arctic land-shelf system is elaborated. Through salinity vs. 224Ra and 224Ra / 223Ra diagrams, the three main SGD-influenced water masses were identified and their end-member composition was constrained. Based on simple mass-balance box models, discharge rates at sites in the submarine permafrost talik zone were 1. 7 × 106 m3 d−1 or 19.9 m3 s−1, which is much higher than the April discharge of the Yana River. Further studies should apply these techniques on a broader scale with the objective of elucidating the relative importance of the SGD transport vector relative to surface freshwater discharge for both water balance and aquatic components such as dissolved organic carbon, carbon dioxide, methane, and nutrients.
ISSN:	1994-0424 1994-0416 1994-0424 1994-0416
DOI:	10.5194/tc-11-2305-2017