The use of Cs and Sr isotopes as tracers in the Arctic Mediterranean Seas

1988 ◽  
Vol 325 (1583) ◽  
pp. 161-176 ◽  
Keyword(s):  
Deep Water ◽  
Thermohaline Circulation ◽  
Atlantic Water ◽  
The Arctic ◽  
Coastal Current ◽  
Intermediate Water ◽  
Sr Isotopes ◽  
Arctic Ice ◽  
Norwegian Coastal Current

The Arctic Mediterranean Seas constitute an oceanic region in which the thermohaline circulation has a strong advective component and deep ventilation processes are very active relative to other oceanic areas. Details of the nature of these circulation and ventilation processes have been revealed through use of Cs and Sr isotopes from bomb-fallout and nuclear-waste sources as ocean tracers. In both cases, their regional input is dominated by advective supply in the Norwegian Atlantic Current and Norwegian Coastal Current, respectively. The different temporal, spatial, and compositional input patterns of these tracers have been used to study different facets of the regional circulation. These input differences and some representative applications of the use of these tracers are reviewed. The data discussed derive from samples collected both from research vessels and from Arctic ice camps. The topics addressed include: ( a ) the role of Arctic Intermediate Water as source, supplying recent surface water to North Atlantic Deep Water via the Denmark Strait overflow; ( b ) deep convective mixing in the Greenland Sea; ( c ) circulation or recirculation of Atlantic water in the Arctic basins; and ( d ) the role of Arctic shelfwaters in the ventilation of intermediate and deep water in the Eurasian and Canadian basins.

Influence of Nordic Seas dynamics on the Atlantic Water propagation and its impacts on sea ice concentration.

2021 ◽  
Author(s):  
Sourav Chatterjee ◽  
Roshin P Raj ◽  
Laurent Bertino ◽  
Nuncio Murukesh
Keyword(s):  
Sea Ice ◽  
Deep Water ◽  
Atlantic Water ◽  
The Arctic ◽  
Deep Water Formation ◽  
Sea Ice Concentration ◽  
Nordic Seas ◽  
Ice Concentration ◽  
Water Formation

<p>Enhanced intrusion of warm and saline Atlantic Water (AW) to the Arctic Ocean (AO) in recent years has drawn wide interest of the scientific community owing to its potential role in ‘Arctic Amplification’. Not only the AW has warmed over the last few decades , but its transfer efficiency have also undergone significant modifications due to changes in atmosphere and ocean dynamics at regional to large scales. The Nordic Seas (NS), in this regard, play a vital role as the major exchange of polar and sub-polar waters takes place in this region. Further, the AW and its significant modification on its way to AO via the Nordic Seas has large scale implications on e.g., deep water formation, air-sea heat fluxes. Previous studies have suggested that a change in the sub-polar gyre dynamics in the North Atlantic controls the AW anomalies that enter the NS and eventually end up in the AO. However, the role of NS dynamics in resulting in the modifications of these AW anomalies are not well studied. Here in this study, we show that the Nordic Seas are not only a passive conduit of AW anomalies but the ocean circulations in the Nordic Seas, particularly the Greenland Sea Gyre (GSG) circulation can significantly change the AW characteristics between the entry and exit point of AW in the NS. Further, it is shown that the change in GSG circulation can modify the AW heat distribution in the Nordic Seas and can potentially influence the sea ice concentration therein. Projected enhanced atmospheric forcing in the NS in a warming Arctic scenario and the warming trend of the AW can amplify the role of NS circulation in AW propagation and its impact on sea ice, freshwater budget and deep water formation.</p>

Role of the Drake Passage in Controlling the Stability of the Ocean’s Thermohaline Circulation

2005 ◽  
Vol 18 (12) ◽  
pp. 1957-1966 ◽  
Author(s):  
Willem P. Sijp ◽  
Matthew H. England
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Deep Water ◽  
Bottom Water ◽  
Multiple Equilibria ◽  
Thermohaline Circulation ◽  
Drake Passage ◽  
Global Ocean ◽  
Intermediate Water

Abstract The role of a Southern Ocean gateway in permitting multiple equilibria of the global ocean thermohaline circulation is examined. In particular, necessary conditions for the existence of multiple equilibria are studied with a coupled climate model, wherein stable solutions are obtained for a range of bathymetries with varying Drake Passage (DP) depths. No transitions to a Northern Hemisphere (NH) overturning state are found when the Drake Passage sill is shallower than a critical depth (1100 m in the model described herein). This preference for Southern Hemisphere sinking is a result of the particularly cold conditions of the Antarctic Bottom Water (AABW) formation regions compared to the NH deep-water formation zones. In a shallow or closed DP configuration, this forces an exclusive production of deep/bottom water in the Southern Hemisphere. Increasing the depth of the Drake Passage sill causes a gradual vertical decoupling in Atlantic circulation, removing the influence of AABW from the upper 2000 m of the Atlantic Ocean. When the DP is sufficiently deep, this shifts the interaction between a North Atlantic Deep Water (NADW) cell and an AABW cell to an interaction between an (shallower) Antarctic Intermediate Water cell and an NADW cell. This latter situation allows transitions to a Northern Hemisphere overturning state.

scholarly journals Characterization of the Atlantic Water and Levantine Intermediate Water in the Mediterranean Sea using Argo Float Data

2021 ◽  
Author(s):  
Giusy Fedele ◽  
Elena Mauri ◽  
Giulio Notarstefano ◽  
Pierre Marie Poulain
Keyword(s):  
Mediterranean Sea ◽  
Thermohaline Circulation ◽  
Internal Variability ◽  
Warming Trend ◽  
Atlantic Water ◽  
Western Mediterranean ◽  
Water Masses ◽  
Intermediate Water ◽  
Starting Point ◽  
The Mediterranean

Abstract. The Atlantic Water (AW) and Levantine Intermediate Water (LIW) are important water masses that play a crucial role in the internal variability of the Mediterranean thermohaline circulation. In particular, their variability and interaction, along with other water masses that characterize the Mediterranean basin, such as the Western Mediterranean Deep Water (WMDW), contribute to modify the Mediterranean Outflow through the Gibraltar Strait and hence may influence the stability of the global thermohaline circulation. This work aims to characterize the AW and LIW in the Mediterranean Sea, taking advantage of the large observational dataset provided by Argo floats from 2001 to 2019. Using different diagnostics, the AW and LIW were identified, highlighting the inter-basin variability and the strong zonal gradient that characterize the two water masses in this marginal sea. Their temporal variability was also investigated focusing on trends and spectral features which constitute an important starting point to understand the mechanisms that are behind their variability. A clear salinification and warming trend have characterized the AW and LIW in the last two decades (~0.007 and 0.008 yr−1; 0.018 and 0.007 °C yr−1, respectively). The salinity and temperature trends found at subbasin scale are in good agreement with previous results. The strongest trends are found in the Adriatic basin in both the AW and LIW properties. A subbasin dependent spectral variability emerges in the AW and LIW salinity timeseries with peaks between 2 and 10 years.

scholarly journals Frontal structures in the West Spitsbergen Current margins

Ocean Science ◽  
2013 ◽  
Vol 9 (6) ◽  
pp. 957-975 ◽  
Author(s):  
W. Walczowski
Keyword(s):  
Thermohaline Circulation ◽  
Baroclinic Instability ◽  
Atlantic Water ◽  
Transport Processes ◽  
The Arctic ◽  
The West ◽  
Jet Streams ◽  
Nordic Seas ◽  
Western Border ◽  
West Spitsbergen

Abstract. The structures of the hydrographic fronts separating the Atlantic-origin waters from ambient waters in the northern Nordic Seas are discussed. Flows of the western and eastern branches of the West Spitsbergen Current create the Atlantic domain borders and maintain these fronts. This work is based on previous research and on investigations carried out in the project DAMOCLES (Developing Arctic Modelling and Observational Capabilities for Long-term Environmental Studies). Most of the observational data were collected during the R/V Oceania cruises. The main focus of the paper is the western border of the Atlantic domain – the Arctic Front, alongfrontal and transfrontal transports, and the front instability and variability. The alongfrontal baroclinic jet streams were described as a significant source of the Atlantic Water and heat in the Nordic Seas. The baroclinic instability and advection of baroclinic eddies which occurs due to this instability were found to be the main transfrontal transport processes. Most of the Atlantic Water transported by the western branch recirculates west and southward. The eastern branch of the West Spitsbergen Current provides most of the Atlantic Water entering the Arctic Ocean. Both processes are very important for the Arctic and global thermohaline circulation.

scholarly journals The Arctic–Atlantic Thermohaline Circulation*

2013 ◽  
Vol 26 (21) ◽  
pp. 8698-8705 ◽  
Author(s):  
Tor Eldevik ◽  
Jan Even Ø. Nilsen
Keyword(s):  
Degrees Of Freedom ◽  
Thermohaline Circulation ◽  
Global Climate ◽  
Atlantic Water ◽  
The Arctic ◽  
Freshwater Input ◽  
Future Change ◽  
Nordic Seas ◽  
Atlantic Thermohaline Circulation ◽  
Northern Branch

Abstract The Atlantic Ocean's thermohaline circulation is an important modulator of global climate. Its northern branch extends through the Nordic Seas to the cold Arctic, a region that appears to be particularly influenced by climate change. A thermohaline circulation is fundamentally concerned with two degrees of freedom. This is in particular the case for the inflow of warm and saline Atlantic Water through the Nordic Seas toward the Arctic that is balanced by two branches of outflow. The authors present an analytical model, rooted in observations, that constrains the strength and structure of this Arctic–Atlantic thermohaline circulation. It is found, maybe surprisingly, that the strength of Atlantic inflow is relatively insensitive to anomalous freshwater input; it mainly reflects changes in northern heat loss. Freshwater anomalies are predominantly balanced by the inflow's partition into estuarine and overturning circulation with southward polar outflow in the surface and dense overflow at depth, respectively. More quantitatively, the approach presented herein provides a relatively simple framework for making closed and consistent inference on the thermohaline circulation's response to observed or estimated past and future change in the northern seas.

scholarly journals Deep-Water Flow over the Lomonosov Ridge in the Arctic Ocean

2005 ◽  
Vol 35 (8) ◽  
pp. 1489-1493 ◽  
Author(s):  
M-L. Timmermans ◽  
P. Winsor ◽  
J. A. Whitehead
Keyword(s):  
Arctic Ocean ◽  
Deep Water ◽  
Thermohaline Circulation ◽  
Global Climate ◽  
Volume Flow Rate ◽  
The Arctic ◽  
Lomonosov Ridge ◽  
Geothermal Heat ◽  
The Arctic Ocean ◽  
Canadian Basin

Abstract The Arctic Ocean likely impacts global climate through its effect on the rate of deep-water formation and the subsequent influence on global thermohaline circulation. Here, the renewal of the deep waters in the isolated Canadian Basin is quanitified. Using hydraulic theory and hydrographic observations, the authors calculate the magnitude of this renewal where circumstances have thus far prevented direct measurements. A volume flow rate of Q = 0.25 ± 0.15 Sv (Sv ≡ 106 m3 s−1) from the Eurasian Basin to the Canadian Basin via a deep gap in the dividing Lomonosov Ridge is estimated. Deep-water renewal time estimates based on this flow are consistent with 14C isolation ages. The flow is sufficiently large that it has a greater impact on the Canadian Basin deep water than either the geothermal heat flux or diffusive fluxes at the deep-water boundaries.

scholarly journals Surface and subsurface Labrador Shelf water mass conditions during the last 6000 years

2020 ◽  
Vol 16 (4) ◽  
pp. 1127-1143
Author(s):  
Annalena A. Lochte ◽  
Ralph Schneider ◽  
Markus Kienast ◽  
Janne Repschläger ◽  
Thomas Blanz ◽  
...  
Keyword(s):  
Deep Water ◽  
Late Holocene ◽  
Thermohaline Circulation ◽  
Sea Water ◽  
Labrador Sea ◽  
Circulation System ◽  
Deep Water Formation ◽  
Holocene Thermal Maximum ◽  
Water Formation

Abstract. The Labrador Sea is important for the modern global thermohaline circulation system through the formation of intermediate Labrador Sea Water (LSW) that has been hypothesized to stabilize the modern mode of North Atlantic deep-water circulation. The rate of LSW formation is controlled by the amount of winter heat loss to the atmosphere, the expanse of freshwater in the convection region and the inflow of saline waters from the Atlantic. The Labrador Sea, today, receives freshwater through the East and West Greenland currents (EGC, WGC) and the Labrador Current (LC). Several studies have suggested the WGC to be the main supplier of freshwater to the Labrador Sea, but the role of the southward flowing LC in Labrador Sea convection is still debated. At the same time, many paleoceanographic reconstructions from the Labrador Shelf focussed on late deglacial to early Holocene meltwater run-off from the Laurentide Ice Sheet (LIS), whereas little information exists about LC variability since the final melting of the LIS about 7000 years ago. In order to enable better assessment of the role of the LC in deep-water formation and its importance for Holocene climate variability in Atlantic Canada, this study presents high-resolution middle to late Holocene records of sea surface and bottom water temperatures, freshening, and sea ice cover on the Labrador Shelf during the last 6000 years. Our records reveal that the LC underwent three major oceanographic phases from the mid- to late Holocene. From 6.2 to 5.6 ka, the LC experienced a cold episode that was followed by warmer conditions between 5.6 and 2.1 ka, possibly associated with the late Holocene thermal maximum. While surface waters on the Labrador Shelf cooled gradually after 3 ka in response to the neoglaciation, Labrador Shelf subsurface or bottom waters show a shift to warmer temperatures after 2.1 ka. Although such an inverse stratification by cooling of surface and warming of subsurface waters on the Labrador Shelf would suggest a diminished convection during the last 2 millennia compared to the mid-Holocene, it remains difficult to assess whether hydrographic conditions in the LC have had a significant impact on Labrador Sea deep-water formation.

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 Frontal structures in the West Spitsbergen Current margins

2013 ◽  
Vol 10 (4) ◽  
pp. 985-1030 ◽  
Author(s):  
W. Walczowski
Keyword(s):  
Thermohaline Circulation ◽  
Baroclinic Instability ◽  
Atlantic Water ◽  
Transport Processes ◽  
The Arctic ◽  
The West ◽  
Western Border ◽  
Hydrographic Fronts ◽  
West Spitsbergen

Abstract. The structures of the hydrographic fronts separating the Atlantic origin waters from ambient waters in the northern Nordic Seas are discussed. Flows of the western and eastern branches of the West Spitsbergen Current create the Atlantic domain borders and maintain these fronts. The work is based on previous research and on investigations in the project DAMOCLES (Developing Arctic Modeling and Observational Capabilities for Long-term Environmental Studies). Most of the observational data were collected during the R/V Oceania cruises. The main focus of the paper is put on the western border of the Atlantic domain – the Arctic Front, along- and transfrontal transports, the front instability and variability. The baroclinic instability and advection of baroclinic eddies which occurs due to this instability were found as the main transfrontal transport processes. Most of the Atlantic Water transported by the western branch recirculates west and southward. The eastern branch of the West Spitsbergen Current provides most of the Atlantic Water entering the Arctic Ocean. Both processes are very important for the Arctic and global Thermohaline Circulation.

scholarly journals Analysis of the Northern Hemisphere Atmospheric Circulation Response to Arctic Ice Reduction Based on Simulation Results

2021 ◽  
Author(s):  
Gennady Platov ◽  
Vladimir Krupchatnikov ◽  
Viacheslav Gradov ◽  
Irina Borovko ◽  
Evgeny Volodin
Keyword(s):  
Northern Hemisphere ◽  
Reduction Process ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Direct Role ◽  
Climate System Model ◽  
Arctic Sea ◽  
South Of Siberia ◽  
Arctic Ice

The amplified Arctic warming is one of several factors influencing atmospheric dynamics. In this work, we consider a series of numerical experiments to identify the direct role of the Arctic sea ice reduction process in forming climatic trends in the northern hemisphere. Aimed at this, we used two more or less independent mechanisms of ice reduction. The first is traditionally associated with increasing the concentration of carbon dioxide in the atmosphere from the historic level of 360 ppm to 450 ppm and 600 ppm. This growth increases air temperature and decreases the ice volume. The second mechanism is associated with a reduction in the reflectivity of ice and snow. We assume that comparing the results of these two experiments allows us to judge the direct role of ice reduction. The most prominent consequences of ice reduction, as a result, were the weakening of temperature gradient at the tropopause level in mid-latitudes, the slower zonal wind at 50-60∘N, intensification of wave activity in Europe, Western America, and Chukotka, and its weakening in the south of Siberia and Kazakhstan. We also consider how climate change may alter regimes such as blocking and stationary Rossby waves. The study used the INM-CM48 climate system model .

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