A 2000 year record of Atlantic Water temperature variability from the Malangen Fjord, northeastern North Atlantic

The Holocene ◽  
2011 ◽  
Vol 21 (7) ◽  
pp. 1049-1059 ◽  
Author(s):  
M. Hald ◽  
G.R. Salomonsen ◽  
K. Husum ◽  
L.J. Wilson
Keyword(s):  
North Atlantic ◽  
Bottom Water ◽  
Atlantic Water ◽  
Temperature Record ◽  
High Accumulation ◽  
Close Coupling ◽  
Carbon Isotopic ◽  
The North ◽  
Reconstructed Temperature ◽  
Cooling Trend

A high-resolution sedimentary record from the subarctic Malangen fjord in northern Norway, northeastern North Atlantic has been investigated in order to reconstruct variations in influx of Atlantic Water for the last 2000 years. The fjord provides a regional oceanographic climatic signal reflecting changes in the North Atlantic heat flux at this latitude because of its deep sill and the relatively narrow adjoining continental shelf. The reconstructions are based on oxygen and carbon isotopic studies of benthic foraminifera from a high accumulation basin in the Malangen fjord, providing subdecadal time resolution. A comparison between instrumental measurements of bottom water temperatures at the core location and the reconstructed temperatures from benthic foraminiferal δ18O for the same time period demonstrates that the stable isotope values reflect the bottom water temperatures very well. The reconstructed temperature record shows an overall decline in temperature of c. 1°C from c. 40 bc to ad 1350. This cooling trend is assumed to be driven by an orbital forced reduction in insolation. Superimposed on the general cooling trend are several periods of warmer or colder temperatures. The long-term fluctuations in the Malangen fjord are concurrent with fluctuations of Atlantic Water in the northern North Atlantic. Although they are not directly comparable, comparisons of atmospheric temperatures and marine records, indicate a close coupling between the climate systems. After ad 1800 the record shows an unprecedented warming within the last 2000 years.

scholarly journals Multidecadal to millennial marine climate oscillations across the Denmark Strait (~ 66° N) over the last 2000 cal yr BP

2014 ◽  
Vol 10 (1) ◽  
pp. 325-343 ◽  
Author(s):  
J. T. Andrews ◽  
A. E. Jennings
Keyword(s):  
North Atlantic ◽  
Low Frequency ◽  
Atlantic Water ◽  
Ice Age ◽  
The North ◽  
Denmark Strait ◽  
Water Stratification ◽  
The North Atlantic Oscillation ◽  
Frequency Variations ◽  
Marine Climate

Abstract. In the area of Denmark Strait (~66° N), the two modes of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are expressed in changes of the northward flux of Atlantic water and the southward advection of polar water in the East Iceland current. Proxies from marine cores along an environmental gradient from extensive to little or no drift ice, capture low frequency variations over the last 2000 cal yr BP. Key proxies are the weight% of calcite, a measure of surface water stratification and nutrient supply, the weight% of quartz, a measure of drift ice transport, and grain size. Records from Nansen and Kangerlussuaq fjords show variable ice-rafted debris (IRD) records but have distinct mineralogy associated with differences in the fjord catchment bedrock. A comparison between cores on either side of the Denmark Strait (MD99-2322 and MD99-2269) show a remarkable millennial-scale similarity in the trends of the weight% of calcite with a trough reached during the Little Ice Age. However, the quartz records from these two sites are quite different. The calcite records from the Denmark Strait parallel the 2000 yr Arctic summer-temperature reconstructions; analysis of the detrended calcite and quartz data reveal significant multi-decadal–century periodicities superimposed on a major environmental shift occurring ca. 1450 AD.

scholarly journals Flow of Antarctic Bottom Water from the Vema Channel 

2020 ◽  
Author(s):  
Eugene G Morozov ◽  
Dmitry I. Frey ◽  
Roman Y. Tarakanov
Keyword(s):  
Continental Slope ◽  
Water Flow ◽  
North Atlantic ◽  
Bottom Water ◽  
The Other ◽  
Antarctic Bottom Water ◽  
The North ◽  
The North Atlantic ◽  
Current Flows ◽  
Western Wall

Abstract We analyze measurements of bottom currents and thermohaline properties of water north of the Vema Channel with the goal to find pathway continuations of Antarctic Bottom Water flow from the Vema Channel into the Brazil Basin. The analysis is based on CTD/LADCP casts north of the Vema Channel. The flow in the deep Vema Channel consists of two branches. The deepest current flows along the bottom in the center of the channel and the other branch flows above the western wall of the channel. We found two smaller channels of the northern continuation of the deeper bottom flow. These flows become weak and almost disappear at a latitude of 25°30’S. The upper current flows at a depth of 4100-4200 m along the continental slope. We traced this current up to 24°S over a distance exceeding 250 km. This branch transports bottom water that eventually fills the deep basins of the North Atlantic.

scholarly journals Atlantic water in the Faroe area: sources and variability

2012 ◽  
Vol 69 (5) ◽  
pp. 802-808 ◽  
Author(s):  
Karin Margretha H. Larsen ◽  
Hjálmar Hátún ◽  
Bogi Hansen ◽  
Regin Kristiansen
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Atlantic Water ◽  
Heat Fluxes ◽  
The North ◽  
Salinity Variability ◽  
Increasing Trend ◽  
The North Atlantic ◽  
Pass Through ◽  
Northeastern Atlantic

Abstract Larsen, K. M. H., Hátún, H., Hansen, B., and Kristiansen, R. 2012. Atlantic water in the Faroe area: sources and variability. – ICES Journal of Marine Science, 69: 802–808. The inflow of Atlantic water (AW) across the Greenland–Scotland Ridge and into the Nordic Seas controls both physical and biological conditions in the northeastern Atlantic through its transport of heat, salt, and other properties. The two main branches of this flow pass through the Iceland–Faroe Gap and the Faroe–Shetland Channel, respectively. Regular monitoring along four standard sections crossing these flows provides time-series of the AW temperature and salinity variability since the late 1980s. The analysis of these series presented shows a persistent increasing trend in both temperature and salinity, modulated by smaller subdecadal oscillations. Using supplementary data sources, the previously established link between the large-scale circulation in the North Atlantic and Atlantic inflow properties is supported. Salinity is also impacted by large changes in the Bay of Biscay source waters, and upstream air–sea heat fluxes modulate temperature. Relationships between changes in transport and associated residence time, and the modifying strength of the air–sea interaction and mixing, are also discussed.

Year-to-year changes in the salinity of the eastern English Channel, 1948–1973: a budget

1981 ◽  
Vol 61 (2) ◽  
pp. 489-507 ◽  
Author(s):  
A. H. Taylor ◽  
P. C. Reid ◽  
T. J. Marsh ◽  
T. D. Jonas ◽  
J. A. Stephens
Keyword(s):  
North Atlantic ◽  
River Runoff ◽  
Atlantic Water ◽  
English Channel ◽  
Local Wind ◽  
Local Data ◽  
The North ◽  
Total Runoff ◽  
Flow Through ◽  
Local Wind Forcing

A model has been used to assess the relative importance of the various factors contributing to changes in the salinity of the eastern English Channel between 1948 and 1973. As part of the data input to the model, monthly means (1948–73) of total runoff into the eastern English Channel and monthly estimates of evaporation and precipitation for the same area (1961–73) were calculated. The results of this study have shown that river runoff is an important factor contributing to the variability of salinity in the eastern English Channel; rainfall over and evaporation from the Channel may also be important at certain times. The model can predict satisfactorily more than 80% of the variation of salinity from local data inputs. While Atlantic water movements and salinities may contribute to variability at the entrance to the English Channel, variations of flow through the Channel, caused by local wind forcing or originating further out in the Atlantic, have little effect on the fluctuations of salinity in the eastern English Channel. Furthermore, fluctuations in the salinity of the North Atlantic do not correspond to those observed at the entrance to the English Channel. River runoff and mixing due to the wind and tides appear to be the main factors responsible for the seasonal changes of salinity in the eastern English Channel.

scholarly journals Multi-decadal to-century NAO-like marine climate oscillations across the Denmark Strait (~66° N) over the last 2000 cal yr BP

2013 ◽  
Vol 9 (4) ◽  
pp. 3871-3917
Author(s):  
J. T. Andrews ◽  
A. E. Jennings
Keyword(s):  
North Atlantic ◽  
Environmental Gradient ◽  
Low Frequency ◽  
Atlantic Water ◽  
The North ◽  
Denmark Strait ◽  
Abrupt Changes ◽  
Water Stratification ◽  
The North Atlantic Oscillation ◽  
Marine Climate

Abstract. In the area of Denmark Strait (~66° N) the two modes of the North Atlantic Oscillation (NAO) are expressed in changes of the northward flux of Atlantic Water and the southward advection of Polar Water in the East Iceland Current. Proxies from marine cores along an environmental gradient from extensive to little or no drift ice, capture low frequency NAO-like variations over the last 2000 cal yr BP. Key proxies are the weight% of calcite, a measure of surface water stratification and nutrient supply, the weight% of quartz, a measure of drift ice transport, and grain-size. Records from Nansen and Kangerlussuaq fjords show variable ice-rafted debris (IRD) records but have distinct mineralogy associated with differences in the fjord catchment bedrock. High-resolution detrended records from Kangerlussuaq Trough show abrupt, significant multi-decadal changes (72 and 56 yr for calcite, and 94 and 65 yr for quartz), and parallel the 2000 yr Arctic summer temperature reconstructions. The calcite minimum occurred ca. 1550 AD whereas the quartz maxima occurred 200 yr earlier. Changes in calcite wt% from N and SW Iceland show similar abrupt changes to those in Kangerlussuaq Trough with an abrupt calcite peak ~1320 AD. Quartz values increased at two N Iceland sites in the last 500 yr whereas values declined in the East Greenland site.

scholarly journals Benthic foraminifera as tracers of brine production in Storfjorden sea ice factory

2019 ◽  
Author(s):  
Eleonora Fossile ◽  
Maria Pia Nardelli ◽  
Arbia Jouini ◽  
Bruno Lansard ◽  
Antonio Pusceddu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Sea Ice ◽  
North Atlantic ◽  
Benthic Foraminifera ◽  
Atlantic Water ◽  
Arctic Seas ◽  
Organic Matter Quality ◽  
Svalbard Archipelago ◽  
The North ◽  
Fresh Organic Matter

Abstract. The rapid response of benthic foraminifera to environmental factors (e.g., organic matter quality and quantity, salinity, pH) and their high fossilisation potential make them promising bio-indicators for the intensity and recurrence of brine formation in Arctic seas. Such approach, however, requires a thorough knowledge of their modern ecology in such extreme settings. To this aim, seven stations along a N–S transect across the Storfjorden (Svalbard archipelago) have been sampled using an interface multicorer. This fjord is an area of intense sea ice formation characterised by the production of Brine-enriched Shelf Waters (BSW) as a result of a recurrent latent-heat polynya. Living (Rose Bengal stained) foraminiferal assemblages were analysed together with geochemical and sedimentological parameters in the top five centimetres of the sediment. Three major biozones were distinguished: (i) the inner fjord dominated by typical glacier proximal calcareous species which opportunistically respond to fresh organic matter inputs; (ii) the deep basins and sill characterised by glacier distal agglutinated faunas. These latter are either dominant because of the mostly refractory nature of organic matter and/or the brine persistence that hampers the growth of calcareous species and/or causes their dissolution. (iii) The outer fjord characterised by typical North Atlantic species due to the intrusion of the North Atlantic water in the Storfjordrenna. The stressful conditions present in the deep basins and sill (i.e. acidic waters and low food quality) result in a high agglutinated/calcareous ratio (A / C). This supports the potential use of the A / C ratio as a proxy for brine persistence and overflow in Storfjorden.

scholarly journals Enhancement of the North Atlantic CO<sub>2</sub> sink by Arctic Waters

2021 ◽  
Vol 18 (5) ◽  
pp. 1689-1701
Author(s):  
Jon Olafsson ◽  
Solveig R. Olafsdottir ◽  
Taro Takahashi ◽  
Magnus Danielsen ◽  
Thorarinn S. Arnarson
Keyword(s):  
North Atlantic ◽  
Thermohaline Circulation ◽  
Atlantic Water ◽  
Water Masses ◽  
The Arctic ◽  
Arctic Water ◽  
The North ◽  
The North Atlantic ◽  
Co2 Sink ◽  
The One

Abstract. The North Atlantic north of 50∘ N is one of the most intense ocean sink areas for atmospheric CO2 considering the flux per unit area, 0.27 Pg-C yr−1, equivalent to −2.5 mol C m−2 yr−1. The northwest Atlantic Ocean is a region with high anthropogenic carbon inventories. This is on account of processes which sustain CO2 air–sea fluxes, in particular strong seasonal winds, ocean heat loss, deep convective mixing, and CO2 drawdown by primary production. The region is in the northern limb of the global thermohaline circulation, a path for the long-term deep-sea sequestration of carbon dioxide. The surface water masses in the North Atlantic are of contrasting origins and character, with the northward-flowing North Atlantic Drift, a Gulf Stream offspring, on the one hand and on the other hand the cold southward-moving low-salinity Polar and Arctic waters with signatures from Arctic freshwater sources. We have studied by observation the CO2 air–sea flux of the relevant water masses in the vicinity of Iceland in all seasons and in different years. Here we show that the highest ocean CO2 influx is to the Arctic and Polar waters, respectively, -3.8±0.4 and -4.4±0.3 mol C m−2 yr−1. These waters are CO2 undersaturated in all seasons. The Atlantic Water is a weak or neutral sink, near CO2 saturation, after poleward drift from subtropical latitudes. These characteristics of the three water masses are confirmed by data from observations covering 30 years. We relate the Polar Water and Arctic Water persistent undersaturation and CO2 influx to the excess alkalinity derived from Arctic sources. Carbonate chemistry equilibrium calculations clearly indicate that the excess alkalinity may support at least 0.058 Pg-C yr−1, a significant portion of the North Atlantic CO2 sink. The Arctic contribution to the North Atlantic CO2 sink which we reveal was previously unrecognized. However, we point out that there are gaps and conflicts in the knowledge about the Arctic alkalinity and carbonate budgets and that future trends in the North Atlantic CO2 sink are connected to developments in the rapidly warming and changing Arctic. The results we present need to be taken into consideration for the following question: will the North Atlantic continue to absorb CO2 in the future as it has in the past?

scholarly journals What Fraction of the Pacific and Indian Oceans' Deep Water is formed in the North Atlantic?

2018 ◽  
Author(s):  
James W. B. Rae ◽  
Wally Broecker
Keyword(s):  
Southern Ocean ◽  
North Atlantic ◽  
Deep Water ◽  
Bottom Water ◽  
Ocean Bottom ◽  
The North ◽  
Water Value ◽  
The Pacific ◽  
Northern Atlantic ◽  
The North Atlantic

Abstract. In this contribution we explore constraints on the fractions of deep water present in Indian and Pacific Oceans which originated in the northern Atlantic and in the Southern Ocean. Based on PO4* we show that if ventilated Antarctic shelf waters characterize the Southern contribution, then the proportions are close to 50–50. If instead a Southern Ocean bottom water value is used, the Southern contribution is increased to 75 %. While this larger estimate may characterize the volume of water entering the Indo-Pacific from the Southern Ocean, it contains a significant portion of entrained northern water. We also note that ventilation may be highly tracer dependent: for instance Southern Ocean waters may contribute only 35 % of the deep radiocarbon budget, even if their volumetric contribution is 75 %. In our estimation, the most promising approaches involve using CFC-11 to constrain the amount of deep water formed in the Southern Ocean.

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