scholarly journals Annual cycle of downward particle fluxes on each side of the Gakkel Ridge in the central Arctic Ocean

2020 ◽  
Vol 378 (2181) ◽  
pp. 20190368 ◽  
Author(s):  
Eva-Maria Nöthig ◽  
Catherine Lalande ◽  
Kirsten Fahl ◽  
Katja Metfies ◽  
Ian Salter ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Arctic Ocean ◽  
Euphotic Zone ◽  
Sediment Traps ◽  
Atlantic Water ◽  
Total Particulate Matter ◽  
Central Arctic Ocean ◽  
Gakkel Ridge ◽  
Particulate Nitrogen ◽  
Lena River

Two mooring arrays carrying sediment traps were deployed from September 2011 to August 2012 at ∼83°N on each side of the Gakkel Ridge in the Nansen and Amundsen Basins to measure downward particle flux below the euphotic zone (approx. 250 m) and approximately 150 m above seafloor at approximately 3500 and 4000 m depth, respectively. In a region that still experiences nearly complete ice cover throughout the year, export fluxes of total particulate matter (TPM), particulate organic carbon (POC), particulate nitrogen (PN), biogenic matter, lithogenic matter, biogenic particulate silica (bPSi), calcium carbonate (CaCO 3 ), protists and biomarkers only slightly decreased with depth. Seasonal variations of particulate matter fluxes were similar on both sides of the Gakkel Ridge. Somewhat higher export rates in the Amundsen Basin and differences in the composition of the sinking TPM and bPSi on each side of the Gakkel Ridge probably reflected the influence of the Lena River/Transpolar Drift in the Amundsen Basin and the influence of Atlantic water in the Nansen Basin. Low variations in particle export with depth revealed a limited influence of lateral advection in the deep barren Eurasian Basin. This article is part of the theme issue ‘The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning’.

Zooplankton Retained in Sequential Sediment Traps along the Beaufort Sea Shelf Break during Winter

1992 ◽  
Vol 49 (4) ◽  
pp. 663-670 ◽  
Author(s):  
J. R. Forbes ◽  
R. W. Macdonald ◽  
E. C. Carmack ◽  
K. Iseki ◽  
M. C. O'Brien
Keyword(s):  
Arctic Ocean ◽  
Zooplankton Community ◽  
Beaufort Sea ◽  
Sediment Traps ◽  
Atlantic Water ◽  
Shelf Break ◽  
The Other ◽  
Calanoid Copepods ◽  
Central Arctic Ocean ◽  
Time Of Year

Zooplankton retained in four sediment traps deployed along the shelf break of the eastern Beaufort Sea, from September 1987 to March 1988, were used to investigate temporal and regional variations of the zooplankton community during winter. Despite trap selectivity, the species composition indicated that both the shelf community and Atlantic water community of the deep Arctic Ocean are excluded from the shelf break at this time of year. There was no evidence of off-shelf transport during the study period. Taxa collected, predominantly pteropods (Spiratella helicina) and calanoid copepods, were typical of the community in the upper 200 m of the central Arctic Ocean. The abundance of pteropods was strongly associated with ice cover. The easternmost trap, located at the entrance to Amundsen Gulf, had a distribution of animals distinct from those in the other traps. It lay outside the influence of the Beaufort Gyre and Beaufort Undercurrent, which apparently affected the other locations.

scholarly journals Scenario Changes of Atlantic Water in the Arctic Ocean

2015 ◽  
Vol 28 (14) ◽  
pp. 5523-5548 ◽  
Author(s):  
Zhenxia Long ◽  
Will Perrie
Keyword(s):  
Climate Change ◽  
Arctic Ocean ◽  
Heat Loss ◽  
Climate Change Scenario ◽  
Climate Model ◽  
Atlantic Water ◽  
Heat Fluxes ◽  
Change Scenario ◽  
Pressure System ◽  
Central Arctic Ocean

Abstract The authors explore possible temperature modifications of the Atlantic Water Layer (AWL) induced by climate change, performing simulations for 1970 to 2099 with a coupled ice–ocean Arctic model (CIOM). Surface fields to drive the CIOM were provided by the Canadian Regional Climate Model (CRCM), driven by outputs from the Canadian Centre for Climate Modelling and Analysis (CCCma) Coupled Global Climate Model, version 3 (CGCM3) following the A1B climate change scenario. In the present climate, represented as 1990–2009, the CIOM can reliably reproduce the AWL compared to Polar Science Center Hydrographic Climatology (PHC) data. For the future climate, assuming the A1B climate change scenario, there is a significant increase in water volume transport into the central Arctic Ocean through Fram Strait due to the weakened atmospheric high pressure system over the western Arctic and an intensified atmospheric low pressure system over the Nordic seas. The AWL temperature tends to decrease from 0.36°C in the 2010s to 0.26°C in the 2060s. In the vertical, the warm Atlantic water core slightly expands before the 2030s, significantly shrinks after the 2050s, and essentially disappears by 2070–99, in the southern Beaufort Sea. The temperature decrease after 2030 is mainly due to the reduced heat fluxes in the Kara and Barents Seas. In the northeastern Barents and Kara Seas, the loss of sea ice increases the heat loss from the Atlantic water and reduces the water temperature near the bottom, contributing to decreased heat fluxes into the central Arctic Ocean, as well as decreased AWL temperature at central Arctic Ocean intermediate layers. In addition, the vertically integrated heat loss also plays an important role in the AWL cooling process.

scholarly journals Central Arctic Ocean paleoceanography from ~ 50 ka to present, on the basis of ostracode faunal assemblages from SWERUS 2014 expedition

2017 ◽  
Author(s):  
Laura Gemery ◽  
Thomas M. Cronin ◽  
Robert K. Poirier ◽  
Christof Pearce ◽  
Natalia Barrientos ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Large Scale ◽  
Late Quaternary ◽  
Atlantic Water ◽  
Environmental Indicators ◽  
The Arctic ◽  
Lomonosov Ridge ◽  
Central Arctic Ocean ◽  
Ice Conditions

Abstract. Late Quaternary paleoceanographic changes in the central Arctic Ocean were reconstructed from a multicore and gravity core from the Lomonosov Ridge (Arctic Ocean) collected during the 2014 SWERUS-C3 Expedition. Ostracode assemblages dated by accelerator mass spectrometry (AMS) indicate changing sea-ice conditions and warm Atlantic Water (AW) inflow to the Arctic Ocean from ~ 50 ka to present. Key taxa used as environmental indicators include Acetabulastoma arcticum (perennial sea ice), Polycope spp. (productivity and sea ice), Krithe hunti (partially sea-ice free conditions, deep water inflow), and Rabilimis mirabilis (high nutrient, AW inflow). Results indicate seasonally sea-ice free conditions during Marine Isotope Stage (MIS) 3 (~ 57–29 ka), rapid deglacial changes in water mass conditions (15–11 ka), seasonally sea-ice free conditions during the early Holocene (~ 10–7 ka) and perennial sea ice during the late Holocene. Comparisons with faunal records from other cores from the Mendeleev and Lomonosov Ridges suggest generally similar patterns, although sea-ice cover during the last glacial maximum may have been less extensive at the southern Lomonosov Ridge at our core site (~ 85.15° N, 152° E) than farther north and towards Greenland. The new data also provide evidence for abrupt, large-scale shifts in ostracode species depth and geographical distributions during rapid climatic transitions.

scholarly journals On the 14C and 39Ar Distribution in the Central Arctic Ocean: Implications for Deep Water Formation

Radiocarbon ◽  
1994 ◽  
Vol 36 (3) ◽  
pp. 327-343 ◽  
Author(s):  
Peter Schlosser ◽  
Bernd Kromer ◽  
Gote Östlund ◽  
Brenda Ekwurzel ◽  
Gerhard Bönisch ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Deep Water ◽  
Atlantic Water ◽  
The Arctic ◽  
Central Arctic Ocean ◽  
Deep Waters ◽  
The Arctic Ocean ◽  
Bottom Waters ◽  
Eurasian Basin ◽  
Canadian Basin

We present ΔA14C and 39Ar data collected in the Nansen, Amundsen and Makarov basins during two expeditions to the central Arctic Ocean (RV Polarstern cruises ARK IV/3, 1987 and ARK VIII/3, 1991). The data are used, together with published Δ14C values, to describe the distribution of Δ14C in all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada Basins), as well as the 39Ar distribution in the Nansen Basin and the deep waters of the Amundsen and Makarov Basins. From the combined Δ14C and 39Ar distributions, we derive information on the mean “isolation ages” of the deep and bottom waters of the Arctic Ocean. The data point toward mean ages of the bottom waters in the Eurasian Basin (Nansen and Amundsen Basins) of ca. 250-300 yr. The deep waters of the Amundsen Basin show slightly higher 3H concentrations than those in the Nansen Basin, indicating the addition of a higher fraction of water that has been at the sea surface during the past few decades. Correction for the bomb 14C added to the deep waters along with bomb 3H yields isolation ages for the bulk of the deep and bottom waters of the Amundsen Basin similar to those estimated for the Nansen Basin. This finding agrees well with the 39Ar data. Deep and bottom waters in the Canadian Basin (Makarov and Canada Basins) are very homogeneous, with an isolation age of ca. 450 yr. Δ14C and 39Ar data and a simple inverse model treating the Canadian Basin Deep Water (CBDW) as one well-mixed reservoir renewed by a mixture of Atlantic Water (29%), Eurasian Basin Deep Water (69%) and brine-enriched shelf water (2%) yield a mean residence time of CBDW of ca. 300 yr.

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.

Zooplankton from the Arctic Ocean and Adjacent Canadian Waters

1965 ◽  
Vol 22 (2) ◽  
pp. 543-564 ◽  
Author(s):  
E. H. Grainger
Keyword(s):  
Surface Layer ◽  
Surface Water ◽  
Arctic Ocean ◽  
Canadian Arctic ◽  
Atlantic Water ◽  
The Arctic ◽  
Central Arctic Ocean ◽  
As Species ◽  
Calanus Glacialis ◽  
The Arctic Ocean

Zooplankton collections from the Arctic Ocean, the Beaufort Sea, and northwestern Canadian coastal waters are described, along with physical characteristics of the waters sampled. About 50 species are included.The collections are compared with records from the central Arctic Ocean and other waters adjacent to the present region. The species are shown to fall into three groups. One is characteristic of the surface water of the Arctic Ocean, one of the Atlantic water and to a lesser extent the deep layer of the surface water of the Arctic Ocean, and one of the shallow peripheral seas of the Arctic Ocean.The surface water group includes eight species which account for more than 95% of the copepod individuals found in the surface layer, and which appear to be the only copepods which breed in the surface layer of the central Arctic Ocean. The same species are the major constituents of the zooplankton found in the waters of the Canadian arctic, from the Arctic Ocean to Davis Strait. The deeper Atlantic species of the Arctic Ocean, more numerous as species but far less numerous as individuals than those of the surface water, occur only very rarely in the surface layers, show no evidence of breeding there, and appear to be almost entirely absent from Canadian archipelago waters inside the shelf. Clear continuity of the Arctic Ocean surface fauna through the waters of the Canadian arctic is shown, along with the almost total exclusion from archipelago waters of the deeper Atlantic fauna. This intrusion of Atlantic species into the waters of arctic Canada appears to be almost entirely restricted to the southeast part of the region, especially Hudson Strait and adjacent waters.Development rates of two copepods in the Arctic Ocean, Microcalanus pygmaeus and Calanus glacialis, are discussed.

scholarly journals Intense photooxidative degradation of planktonic and bacterial lipids in sinking particles collected with sediment traps across the Canadian Beaufort Shelf (Arctic Ocean)

2012 ◽  
Vol 9 (11) ◽  
pp. 4787-4802 ◽  
Author(s):  
J.-F. Rontani ◽  
B. Charriere ◽  
A. Forest ◽  
S. Heussner ◽  
F. Vaultier ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Arctic Ocean ◽  
Heterotrophic Bacteria ◽  
Euphotic Zone ◽  
Sediment Traps ◽  
The Arctic ◽  
Wax Ester ◽  
Type Ii ◽  
Sinking Particles ◽  
Biotic Degradation

Abstract. The lipid content of seven samples of sinking particles collected with sediment traps moored at ~ 100 m depth in summer and fall across the Canadian Beaufort Shelf (Arctic Ocean) was investigated. Our main goal was to quantify and characterize the biotic and abiotic degradation processes that acted on sinking material during these periods. Diatoms, which dominated the phytoplanktonic assemblage in every trap sample, appeared to be remarkably sensitive to Type II (i.e. involving singlet oxygen) photodegradation processes in summer, but seemed to be relatively unaffected by biotic degradation at the same time. Hence, the relative recalcitrance of phytodetritus towards biodegradation processes during the Arctic midnight sun period was attributed to the strong photodegradation state of heterotrophic bacteria, which likely resulted from the efficient transfer of singlet oxygen from photodegraded phytoplanktonic cells to attached bacteria. In addition, the detection in trap samples of photoproducts specific to wax ester components found in herbivorous copepods demonstrated that zooplanktonic faecal material exported out of the euphotic zone in summer were affected by Type II photodegradation processes as well. By contrast, sinking particles collected during the autumn were not influenced by any light-driven stress. Further chemical analyses showed that photodegraded sinking particles contained an important amount of intact hydroperoxides, which could then induce a strong oxidative stress in underlying sediments.

scholarly journals Arctic Ocean Warming Contributes to Reduced Polar Ice Cap

2010 ◽  
Vol 40 (12) ◽  
pp. 2743-2756 ◽  
Author(s):  
Igor V. Polyakov ◽  
Leonid A. Timokhov ◽  
Vladimir A. Alexeev ◽  
Sheldon Bacon ◽  
Igor A. Dmitrenko ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Atlantic Water ◽  
Ocean Model ◽  
The Arctic ◽  
Ice Thickness ◽  
Polar Ice ◽  
Central Arctic Ocean ◽  
Ice Cap ◽  
1D Model ◽  
Eurasian Basin

Abstract Analysis of modern and historical observations demonstrates that the temperature of the intermediate-depth (150–900 m) Atlantic water (AW) of the Arctic Ocean has increased in recent decades. The AW warming has been uneven in time; a local ∼1°C maximum was observed in the mid-1990s, followed by an intervening minimum and an additional warming that culminated in 2007 with temperatures higher than in the 1990s by 0.24°C. Relative to climatology from all data prior to 1999, the most extreme 2007 temperature anomalies of up to 1°C and higher were observed in the Eurasian and Makarov Basins. The AW warming was associated with a substantial (up to 75–90 m) shoaling of the upper AW boundary in the central Arctic Ocean and weakening of the Eurasian Basin upper-ocean stratification. Taken together, these observations suggest that the changes in the Eurasian Basin facilitated greater upward transfer of AW heat to the ocean surface layer. Available limited observations and results from a 1D ocean column model support this surmised upward spread of AW heat through the Eurasian Basin halocline. Experiments with a 3D coupled ice–ocean model in turn suggest a loss of 28–35 cm of ice thickness after ∼50 yr in response to the 0.5 W m−2 increase in AW ocean heat flux suggested by the 1D model. This amount of thinning is comparable to the 29 cm of ice thickness loss due to local atmospheric thermodynamic forcing estimated from observations of fast-ice thickness decline. The implication is that AW warming helped precondition the polar ice cap for the extreme ice loss observed in recent years.

scholarly journals Intense photooxidative degradation of planktonic and bacterial lipids in sinking particles collected with sediment traps across the Canadian Beaufort Shelf (Arctic Ocean)

2012 ◽  
Vol 9 (6) ◽  
pp. 7743-7781 ◽  
Author(s):  
J.-F. Rontani ◽  
B. Charriere ◽  
A. Forest ◽  
S. Heussner ◽  
F. Vaultier ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Arctic Ocean ◽  
Heterotrophic Bacteria ◽  
Euphotic Zone ◽  
Sediment Traps ◽  
The Arctic ◽  
Wax Ester ◽  
Type Ii ◽  
Sinking Particles ◽  
Biotic Degradation

Abstract. The lipid content of seven samples of sinking particles collected with sediment traps moored at ~100 m depth in summer and fall across the Canadian Beaufort Shelf (Arctic Ocean) was investigated. Our main goal was to quantify and characterize the biotic and abiotic degradation processes that acted on sinking material during these periods. Diatoms, which dominated the phytoplanktonic assemblage in every trap sample, appeared to be remarkably sensitive to Type II (i.e. involving singlet oxygen) photodegradation processes in summer, but seemed to be relatively unaffected by biotic degradation at the same time. Hence, the relative recalcitrance of phytodetritus towards biodegradation processes during the Arctic midnight sun period was attributed to the strong photodegradation state of heterotrophic bacteria, which likely resulted from the efficient transfer of singlet oxygen from photodegraded phytoplanktonic cells to attached bacteria. In addition, the detection in trap samples of photoproducts specific to wax ester components found in herbivorous copepods demonstrated that zooplanktonic faecal material exported out of the euphotic zone in summer were as well affected by Type II photodegradation processes. By contrast, sinking particles collected during the autumn were not influenced by any light-driven stress. Further chemical analyses showed that photodegraded sinking particles contained an important amount of intact hydroperoxides, which could then induce a strong oxidative stress in underlying sediments.

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