scholarly journals Stability of North Atlantic water masses in face of pronounced climate variability during the Pleistocene

2004 ◽  
Vol 19 (2) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. E. Raymo ◽  
D. W. Oppo ◽  
B. P. Flower ◽  
D. A. Hodell ◽  
J. F. McManus ◽  
...  
Keyword(s):  
Climate Variability ◽  
North Atlantic ◽  
Atlantic Water ◽  
Water Masses ◽  
North Atlantic Water

scholarly journals Paleoenvironments along the Eastern Laurentide Ice Sheet Margin and Timing of the Last Ice Maximum and Retreat

2008 ◽  
Vol 41 (2) ◽  
pp. 265-277 ◽  
Author(s):  
Anne de Vernal ◽  
Claude Hillaire-Marcel
Keyword(s):  
Late Pleistocene ◽  
North Atlantic ◽  
Environmental Changes ◽  
Atlantic Water ◽  
Polar Front ◽  
Water Masses ◽  
Labrador Sea ◽  
Eastern Canada ◽  
North Atlantic Water ◽  
Late Wisconsinan

ABSTRACT Palynological and isotopic analysis in a few deep-sea cores from the Labrador Sea reveals strong environmental changes related to the Late Pleistocene glacial fluctuations over eastern Canada. On the whole, the Labrador Sea was characterized by strong exchanges between North Atlantic water masses, Arctic outflows, and meltwater discharges from Laurentide, Greenland and lnuitian ice sheets. The penetration of temperate Atlantic waters persisted throughout most of the Late Pleistocene, with a brief interruption during the Late Wisconsinan. During this glacial substage, a slight but continuous meltwater runoff from the Laurentide ice margins grounded on the northern Labrador Shelf is indicated by relatively low 18O values and low-salinity (< 30‰) dinocyst assemblages. The calving of the ice margin, the melwater outflow and the subsequent dilution of surface waters offshore Labrador probably contributed to the dispersal of floating ice and, consequently, to a southward displacement of the polar front restraining the penetration of North Atlantic waters into the Labrador Sea. The advection of southern air masses along the Laurentide ice margins, shown by pollen assemblages, was favourable to abundant precipitation and therefore, high ice accumulation rates, especially over northern Labrador during the Late Wisconsinan. The déglaciation is marked by a brief, but significant, melting event of northern Laurentide ice shortly after 17 ka. The main glacial retreat occurred after ca. 11 ka. It allowed restoration of WSW-ENE atmospheric trajectories, increased phytoplanktonic productivity, and penetration of North Atlantic water masses into the Labrador Sea.

Water masses and mesoscale circulation of North Rockall Trough waters during JASIN 1978

1983 ◽  
Vol 308 (1503) ◽  
pp. 231-252 ◽  
Keyword(s):  
North Atlantic ◽  
Atlantic Water ◽  
Water Masses ◽  
Reference Level ◽  
Intermediate Water ◽  
Norwegian Sea ◽  
The North ◽  
North Atlantic Water ◽  
Rockall Trough ◽  
North Rockall Trough

During the Joint Air-Sea Interaction Experiment (JASIN 1978) grids of temperature and salinity profiles were worked within an area of about 150 km x 150 km to obtain details of the mesoscale circulation around the location of the experiment in the North Rockall Trough. Data were also obtained from moored current meters and from research vessel observations in the surrounding waters. In the uppermost layers two water masses were present, North Atlantic Water from southern parts of the Rockall Trough and fresher Modified North Atlantic Water from the north and west. Beneath these an intermediate water formed by Atlantic Water in contact with Subarctic Intermediate Water was found and at greater depth distinctions could be drawn between water from the south, water with an admixture of Norwegian Sea Deep Water from the Scotland-Iceland ridges and, more sparse, water with a component of Arctic Intermediate Water from the Faroe-Shetland Channel. The patterns of circulation were found to change little between the lower depths and 200 m. An anticyclonic eddy of fresher, colder water moved westwards across the northern half of the grid at about 1.4 km day-1, the northern sector of a more saline meander expanded westwards across the southern part of the area, and smaller less well resolved circulations were found in the west. The eddy contained water of overflow origin and the meander appears to have been part of the main Atlantic to Norwegian Sea current. When inverse analysis was applied to two of the data sets to investigate choices of reference level, zero velocity at the bottom gave the only physically realistic solution. Although the necessary process of averaging the observations to data points 45 km apart obscured the resolution of smaller features, confidence in the reference level that satisfied the inverse analysis allowed classical geostrophic analysis to be performed on the full set of stations, supporting and quantifying the earlier analysis of patterns. The influence of the deeper circulation can be seen in the modification of the thermohaline structure in the seasonal thermocline and mixed layers. Boundaries between adjacent upper water masses were distorted by underlying convergences or fragmented by horizontal shears.

Exploratory analyses of trichlorofluoromethane (F-11) in North Atlantic water columns

1978 ◽  
Vol 5 (8) ◽  
pp. 645-648 ◽  
Author(s):  
Paul M. Hammer ◽  
J. M. Hayes ◽  
W. J. Jenkins ◽  
R. B. Gagosian
Keyword(s):  
North Atlantic ◽  
Atlantic Water ◽  
Water Columns ◽  
North Atlantic Water

scholarly journals Declining silicate concentrations in the Norwegian and Barents Seas

2012 ◽  
Vol 69 (2) ◽  
pp. 208-212 ◽  
Author(s):  
Francisco Rey
Keyword(s):  
North Atlantic ◽  
Relative Proportion ◽  
Atlantic Water ◽  
Water Masses ◽  
Source Water ◽  
Marine Science ◽  
Norwegian Sea

Abstract Rey, F. 2012. Declining silicate concentrations in the Norwegian and Barents Seas. – ICES Journal of Marine Science, 69: 208–212. Since 1990, a decline in silicate concentrations together with increasing salinities has been observed in the Atlantic water of the Norwegian and Barents Seas. This decline in silicate has been found to be related to the relative proportion in which eastern and western source water masses from the northeastern North Atlantic enter the Norwegian Sea.

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 Export of ice sheet meltwater from Upernavik Fjord, West Greenland

2021 ◽  
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
North Atlantic Ocean ◽  
Atlantic Water ◽  
Water Masses ◽  
Buoyant Plume ◽  
Freshwater Input ◽  
The North ◽  
Freshwater Source ◽  
Lateral Mixing

Abstract Meltwater from Greenland is an important freshwater source for the North Atlantic Ocean, released into the ocean at the head of fjords in the form of runoff, submarine melt and icebergs. The meltwater release gives rise to complex in-fjord transformations that result in its dilution through mixing with other water masses. The transformed waters, which contain the meltwater, are exported from the fjords as a new water mass “Glacially Modified Water” (GMW). Here we use summer hydrographic data collected from 2013 to 2019 in Upernavik, a major glacial fjord in northwest Greenland, to describe the water masses that flow into the fjord from the shelf and the exported GMWs. Using an Optimum Multi-Parameter technique across multiple years we then show that GMW is composed of 57.8 ±8.1% Atlantic Water, 41.0 ±8.3% Polar Water, 1.0 ±0.1% subglacial discharge and 0.2 ±0.2% submarine meltwater. We show that the GMW fractional composition cannot be described by buoyant plume theory alone since it includes lateral mixing within the upper layers of the fjord not accounted for by buoyant plume dynamics. Consistent with its composition, we find that changes in GMW properties reflect changes in the AW and PW source waters. Using the obtained dilution ratios, this study suggests that the exchange across the fjord mouth during summer is on the order of 50 mSv (compared to a freshwater input of 0.5 mSv). This study provides a first order parameterization for the exchange at the mouth of glacial fjords for large-scale ocean models.

scholarly journals Observed trends of anthropogenic acidification in North Atlantic water masses

2012 ◽  
Vol 9 (3) ◽  
pp. 3003-3030
Author(s):  
M. Vázquez-Rodríguez ◽  
F. F. Pérez ◽  
A. Velo ◽  
A. F. Ríos ◽  
H. Mercier
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Deep Convection ◽  
Temporal Trends ◽  
Atlantic Water ◽  
Water Masses ◽  
The North ◽  
Iceland Basin ◽  
The North Atlantic ◽  
Atmospheric Co2 Concentrations

Abstract. The lack of observational pH data has made difficult assessing recent rates of ocean acidification, particularly in the high latitudes. Here we present a time series of high-quality carbon system measurements in the North Atlantic, comprising fourteen cruises spanning over 27 yr (1981–2008) and covering important water mass formation areas like the Irminger and Iceland basins. We provide direct quantification of anthropogenic acidification rates in upper and intermediate North Atlantic waters by removing the natural variability of pH from the observations. Bottle data were normalised to basin-average conditions using climatological data and further condensed into averages per water mass and year to examine the temporal trends. The highest acidification rates of all inspected water masses were associated with surface waters in the Irminger Sea (−0.0018 ± 0.0001 yr−1) and the Iceland Basin (−0.0012 ± 0.0002 yr−1) and, unexpectedly, with Labrador Seawater (LSW) which experienced an unprecedented pH drop of −0.0015 ± 0.001 yr−1. The latter stems from the formation by deep convection and the rapid propagation in the North Atlantic subpolar gyre of this well-ventilated water mass. The high concentrations of anthropogenic CO2 are effectively transported from the surface into intermediate waters faster than via downward diffusion, thus accelerating the acidification rates of LSW. An extrapolation of the observed lineal trends of acidification suggests that the pH of LSW could drop 0.45 units with respect to pre-industrial levels by the time atmospheric CO2 concentrations double the present ones.

scholarly journals Role of cabbeling in water densification in the Greenland Basin

2008 ◽  
Vol 5 (3) ◽  
pp. 507-543
Author(s):  
Y. Kasajima ◽  
T. Johannessen
Keyword(s):  
North Atlantic ◽  
Maximum Velocity ◽  
Atlantic Water ◽  
The Arctic ◽  
Greenland Sea ◽  
Water Types ◽  
North Atlantic Water ◽  
Greenland Basin ◽  
Eastern Periphery ◽  
Induced Velocity

Abstract. The contribution of cabbeling mixing to water mass modification in the Greenland Sea was explored from hydrographic observation across the Greenland Basin in summer 2006. Neutral surface was chosen as a reference frame, and the strength of cabbeling mixing was determined by the dianeutral velocity magnitude. Water types in the area were classified into North Atlantic Water (NAW), modified North Atlantic Water (mNAW), water from Barents Sea near Bear Island (BIW), Arctic Intermediate Water (AIW) and Deep Water (DW), and significant cabbeling-induced velocity (>1 m/day) appeared at the interfaces of these water types below the seasonal pycnocline. The mixing between BIW and NAW in the eastern periphery was the most vigorous, where mixing-induced velocity reached 7.5 m/day which accompanied NAW production of 123 m3/day through transformation of BIW. Cabbeling in the Arctic Frontal Zone was found of two types; mixing within NAW in the upper layer and mixing within mNAW in the lower layer with a maximum velocity of 3 m/day. Source waters in the central Greenland Basin were AIW and mNAW and produced a vertical velocity of 4 m/day. In the western part of the Greenland Basin, the areas of active cabbeling were widely separated and each mixing point appeared rather weak, with a maximum velocity of 2.5 m/day. The average density gain in the eastern periphery was 0.003 kg/m3 while it was 0.001 kg/m3 in the other areas, though the impact of cabbeling on the bulk buoyancy change was highest in the western Greenland Sea. The frontal areas occupied approximately 50% of the whole analysis area and the total density gain due to cabbeling mixing in the Greenland Basin as a whole was estimated as 6.7×10−4 kg/m3.

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