scholarly journals Decrease in <sup>230</sup>Th in the Amundsen Basin since 2007: far-field effect of increased scavenging on the shelf?

Ocean Science ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 221-234
Author(s):  
Ole Valk ◽  
Michiel M. Rutgers van der Loeff ◽  
Walter Geibert ◽  
Sandra Gdaniec ◽  
S. Bradley Moran ◽  
...  
Keyword(s):  
Water Column ◽  
Field Effect ◽  
Sulfur Hexafluoride ◽  
Barents Sea ◽  
Ventilation Rate ◽  
Concomitant Increase ◽  
Central Arctic Ocean ◽  
The Barents Sea ◽  
Circulation Change ◽  
Atlantic Origin

Abstract. This study provides dissolved and particulate 230Th and 232Th results as well as particulate 234Th data collected during expeditions to the central Arctic Ocean (GEOTRACES, an international project to identify processes and quantify fluxes that control the distributions of trace elements; sections GN04 and GIPY11). Constructing a time series of dissolved 230Th from 1991 to 2015 enables the identification of processes that control the temporal development of 230Th distributions in the Amundsen Basin. After 2007, 230Th concentrations decreased significantly over the entire water column, particularly between 300 and 1500 m. This decrease is accompanied by a circulation change, evidenced by a concomitant increase in salinity. A potentially increased inflow of water of Atlantic origin with low dissolved 230Th concentrations leads to the observed depletion in dissolved 230Th in the central Arctic. Because atmospherically derived tracers (chlorofluorocarbon (CFC), sulfur hexafluoride (SF6)) do not reveal an increase in ventilation rate, it is suggested that these interior waters have undergone enhanced scavenging of Th during transit from Fram Strait and the Barents Sea to the central Amundsen Basin. The 230Th depletion propagates downward in the water column by settling particles and reversible scavenging.

scholarly journals Circulation changes in the Amundsen Basin from 1991 to 2015 revealed from distributions of dissolved <sup>230</sup>Th

2019 ◽  
Author(s):  
Ole Valk ◽  
Michiel M. Rutgers van der Loeff ◽  
Walter Geibert ◽  
Sandra Gdaniec ◽  
S. Bradley Moran ◽  
...  
Keyword(s):  
Water Column ◽  
Large Scale ◽  
Barents Sea ◽  
Temporal Evolution ◽  
Ventilation Rate ◽  
Concomitant Increase ◽  
Central Arctic Ocean ◽  
The Barents Sea ◽  
Circulation Change ◽  
Atlantic Origin

Abstract. This study provides dissolved and particulate 230Th and 232Th results as well as particulate 234Th data collected during expeditions to the central Arctic Ocean on ARK-XXIX/3 (2015) and ARK-XXII/2 (2007) (GEOTRACES sections GN04 and GIPY11, respectively). Constructing a time-series of dissolved 230Th from 1991 to 2015 enables the identification of processes that control the temporal development of 230Th distributions in the Amundsen Basin. After 2007, 230Th concentrations decreased significantly over the entire water column, particularly between 300 m and 1500 m. This decrease is accompanied by a circulation change, evidenced by a concomitant increase in salinity. Potentially increased inflow of water of Atlantic origin with low dissolved 230Th concentrations leads to the observed depletion in dissolved 230Th in the central Arctic. Because atmospherically derived tracers (CFC, 3He/3H) do not reveal an increase in ventilation rate, it is suggested that these interior waters have undergone enhanced scavenging of Th during transit from the Fram Strait and the Barents Sea to the central Amundsen Basin. The 230Th depletion propagates downward in the water column by settling particles and reversible scavenging. Taken together, the temporal evolution of Th distributions point to significant changes in the large-scale circulation of the Amundsen Basin.

Biogeochemical processes in the Barents sea

2021 ◽  
pp. 287-306
Author(s):  
A.Yu. Lein ◽  
◽  
A.S. Savvichev ◽  
Keyword(s):  
Organic Matter ◽  
Water Column ◽  
Methane Concentration ◽  
Barents Sea ◽  
Biogeochemical Processes ◽  
Total Abundance ◽  
The North ◽  
The Barents Sea ◽  
Continental Origin ◽  
Biomass Of Microorganisms

Biogeochemical processes involving microorganisms play an important role in marine sedimentogenesis. The study of biogeochemical processes in the Barents Sea was carried out from 1997 with interruptions until 2019. Using a complex of geological-geochemical, microbiological, radioisotope and stable isotope methods, it was possible to obtain a quantitative estimate of the total abundance and biomass of microorganisms, rates of biogeochemical processes, methane content and organic matter suspended. In the course of work in four expeditions, it was found that in the surface (0–10 m) water column south of 74° N the magnitude of the total abundance and the biomass of microorganisms increased by 2019 by about 5 times compared to 1998. To the north, in colder waters, the total abundance and the biomass of organisms were lower than in the southern region of the sea. The methane concentration in the surface layer of the water column at the border with the atmosphere did not change much for 20 years (1976–1997) and increased noticeably from 1997 to 2017, from 3.3 to 15.8 nM. The increase in FFM, the biomass of organisms and the concentration of methane in the water column is associated with the melting of glaciers, with the release of organic matter of continental origin released from ice into the water. The results of the work indicate changes in the ecosystem of the Barents Sea.

scholarly journals Inflow of Atlantic-origin waters to the Barents Sea along glacial troughs

Oceanologia ◽  
2009 ◽  
Vol 51 (3) ◽  
pp. 321-340 ◽  
Author(s):  
Gennady G. Matishov ◽  
Dmitry G. Matishov ◽  
Denis V. Moiseev
Keyword(s):  
Barents Sea ◽  
The Barents Sea ◽  
Atlantic Origin

Transformation of Atlantic Water in the Barents Sea in winter: overview of “Transarctika-2019” cruise results

2020 ◽  
Author(s):  
Vladimir Ivanov ◽  
Ivan Frolov ◽  
Kirill Filchuk
Keyword(s):  
Characteristic Feature ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Water Column ◽  
Barents Sea ◽  
Atlantic Water ◽  
The Arctic ◽  
The Barents Sea ◽  
Open Sea ◽  
The Arctic Ocean

&lt;p&gt;In the recent few years the topic of accelerated sea ice loss, and related changes in the vertical structure of water masses in the East-Atlantic sector of the Arctic Ocean, including the Barents Sea and the western part of the Nansen Basin, has been in the foci of multiple studies. This region even earned the name the &amp;#8220;Arctic warming hotspot&amp;#8221;, due to the extreme retreat of sea ice and clear signs of change in the vertical hydrographic structure from the Arctic type to the sub-Arctic one. A gradual increase in temperature and salinity in this area has been observed since the mid-2000s. This trend is hypothetically associated with a general decrease in the volume of sea ice in the Arctic Ocean, which leads to a decrease of ice import in the Barents Sea, salinization, weakening of density stratification, intensification of vertical mixing and an increase of heat and salt fluxes from the deep to the upper mixed layer. The result of such changes is a further reduction of sea ice, i.e. implementation of positive feedback, which is conventionally refereed as the &amp;#8220;atlantification. Due to the fact that the Barents Sea is a relatively shallow basin, the process of atlantification might develop here much faster than in the deep Nansen Basin. Thus, theoretically, the hydrographic regime in the northern part of the Barents Sea may rapidly transform to a &amp;#8220;Nordic Seas &amp;#8211; wise&amp;#8221;, a characteristic feature of which is the year-round absence of the ice cover with debatable consequences for the climate and ecosystem of the region and adjacent land areas. Due to the obvious reasons, historical observations in the Barents Sea mostly cover the summer season. Here we present a rare oceanographic data, collected during the late winter - early spring in 2019. Measurements were occupied at four sequential oceanographic surveys from the boundary between the Norwegian Sea and the Barents Sea &amp;#8211; the so called Barents Sea opening to the boundary between the Barents Sea and the Kara Sea. Completed hydrological sections allowed us to estimate the contribution of the winter processes in the Atlantic Water transformation at the end of the winter season. Characteristic feature of the observed transformation is the homogenization of the near-to-bottom part of the water column with remaining stratification in the upper part. A probable explanation of such changes is the dominance of shelf convection and cascading of dense water over the open sea convection. In this case, complete homogenization of the water column does not occur, since convection in the open sea is impeded by salinity and density stratification, which is maintained by melting of the imported sea ice in the relatively warm water. The study was supported by RFBR grant # 18-05-60083.&lt;/p&gt;

scholarly journals Nitrate assimilation and regeneration in the Barents Sea: insights from nitrogen isotopes

2020 ◽  
Author(s):  
Robyn E. Tuerena ◽  
Joanne Hopkins ◽  
Raja S. Ganeshram ◽  
Louisa Norman ◽  
Camille de la Vega ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Barents Sea ◽  
Nitrogen Isotopes ◽  
Nitrate Assimilation ◽  
Arctic Basin ◽  
Nutrient Supply ◽  
The Arctic ◽  
Central Arctic Ocean ◽  
Particulate Nitrogen ◽  
The Barents Sea

Abstract. While the entire Arctic Ocean is warming rapidly, the Barents Sea in particular is experiencing significant warming and sea ice retreat. An increase in ocean heat transport from the Atlantic is causing the Barents Sea to be transformed from a cold, salinity stratified system into a warmer, less-stratified Atlantic-dominated climate regime. Productivity in the Barents Sea shelf is fuelled by waters of Atlantic origin (AW), which are ultimately exported to the Arctic basin. The consequences of this current regime shift on the nutrient characteristics of the Barents Sea are poorly defined. Here we use the stable isotopic ratios of nitrate (δ15N-NO3, δ18O-NO3), to determine the uptake and modification of AW nutrients in the Barents Sea. In summer months, phytoplankton consume nitrate, surface waters become nitrate depleted, and particulate nitrogen (δ15N-PN) reflects the AW nitrate source. The ammonification of organic matter in shallow sediments resupplies N to the water column through the season. Low δ18O-NO3 in the northern Barents Sea reveals that the nitrate in lower temperature Arctic Waters is > 80 % regenerated through seasonal nitrification. During on shelf nutrient uptake and regeneration, there is no significant change to δ15N-NO3 or N*, suggesting benthic denitrification does not impart an isotopic imprint on pelagic nitrate. Our results demonstrate that the Barents Sea is distinct from other Arctic shelves, where coupled partial nitrification-denitrification enriches δ15N-NO3 and decreases N*. Our results suggest that any current or future changes to productivity on the Barents Sea shelf are unlikely to alter the magnitude or isotopic signature of nutrient supply exported to the central Arctic basin. However, we suggest that the AW nutrient source ultimately determines Barents Sea productivity and changes to this supply may alter Barents Sea primary production and subsequent nutrient supply to the central Arctic Ocean.

scholarly journals Bacterioplankton`s structural characteristics of the Kola and Motovskiy bays in October 2017.

2020 ◽  
Vol 11 (5-2020) ◽  
pp. 27-37
Author(s):  
A.V. Vashchenko ◽  
◽  
T.M. Maksimovskaya ◽  
Keyword(s):  
Water Column ◽  
Trophic Status ◽  
Barents Sea ◽  
Structural Characteristics ◽  
Bacterial Cells ◽  
Quantitative Parameters ◽  
The Barents Sea ◽  
Morphological Composition

The work contains the results of autumn bacterioplankton studies in the coast of the Barents Sea on the example of the Kola and Motovskiybays. Hydrobiological conditions are described. New data on the abundance, biomass, and size and morphological composition of bacterial cells are presented. The distribution of quantitative parameters in the water column was studied. The trophic status of the water areas of the bays was determined.

scholarly journals Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes

2021 ◽  
Vol 18 (2) ◽  
pp. 637-653
Author(s):  
Robyn E. Tuerena ◽  
Joanne Hopkins ◽  
Raja S. Ganeshram ◽  
Louisa Norman ◽  
Camille de la Vega ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Barents Sea ◽  
Nitrate Assimilation ◽  
Arctic Basin ◽  
Significant Loss ◽  
The Arctic ◽  
N Availability ◽  
Central Arctic Ocean ◽  
Particulate Nitrogen ◽  
The Barents Sea

Abstract. While the entire Arctic Ocean is warming rapidly, the Barents Sea in particular is experiencing significant warming and sea ice retreat. An increase in ocean heat transport from the Atlantic is causing the Barents Sea to be transformed from a cold, salinity-stratified system into a warmer, less-stratified Atlantic-dominated climate regime. Productivity in the Barents Sea shelf is fuelled by waters of Atlantic origin (AW) which are ultimately exported to the Arctic Basin. The consequences of this current regime shift on the nutrient characteristics of the Barents Sea are poorly defined. Here we use the stable isotopic ratios of nitrate (δ15N-NO3, δ18O-NO3) to determine the uptake and modification of AW nutrients in the Barents Sea. In summer months, phytoplankton consume nitrate, surface waters become nitrate depleted, and particulate nitrogen (δ15N-PN) reflects the AW nitrate source. The ammonification of organic matter in shallow sediments resupplies N to the water column and replenishes the nitrate inventory for the following season. Low δ18O-NO3 in the northern Barents Sea reveals that the nitrate in lower-temperature Arctic waters is > 80 % regenerated through seasonal nitrification. During on-shelf nutrient uptake and regeneration, there is no significant change to δ15N-NO3 or N*, suggesting that benthic denitrification does not impart an isotopic imprint on pelagic nitrate. Our results demonstrate that the Barents Sea is distinct from other Arctic shelves where benthic denitrification enriches δ15N-NO3 and decreases N*. As nutrients are efficiently recycled in the Barents Sea and there is no significant loss of N through benthic denitrification, changes to Barents Sea productivity are unlikely to alter N availability on shelf or the magnitude of N advected to the central Arctic Basin. However, we suggest that the AW nutrient source ultimately determines Barents Sea productivity and that changes to AW delivery have the potential to alter Barents Sea primary production and subsequent nutrient supply to the central Arctic Ocean.

Sign in / Sign up

Export Citation Format

Share Document