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 Observed acidification trends in North Atlantic water masses

2012 ◽  
Vol 9 (12) ◽  
pp. 5217-5230 ◽  
Author(s):  
M. Vázquez-Rodríguez ◽  
F. F. Pérez ◽  
A. Velo ◽  
A. F. Ríos ◽  
H. Mercier
Keyword(s):  
North Atlantic ◽  
Surface Waters ◽  
Sea Water ◽  
Deep Convection ◽  
Atlantic Water ◽  
Atmospheric Co2 ◽  
Emission Rates ◽  
The North ◽  
Iceland Basin ◽  
The North Atlantic

Abstract. The lack of observational pH data has made it difficult to assess recent rates of ocean acidification, particularly in the high latitudes. Here we present a time series that spans over 27 yr (1981–2008) of high-quality carbon system measurements in the North Atlantic, which comprises fourteen cruises and covers the important water mass formation areas of the Irminger and Iceland Basins. We provide direct quantification of acidification rates in upper and intermediate North Atlantic waters. The highest rates were associated with surface waters and with Labrador Sea Water (LSW). The Subarctic Intermediate and Subpolar Mode Waters (SAIW and SPMW) showed acidification rates of −0.0019 ± 0.0001 and −0.0012 ± 0.0002 yr−1, respectively. The deep convection activity in the North Atlantic Subpolar Gyre injects surface waters loaded with anthropogenic CO2 into lower layers, provoking the remarkable acidification rate observed for LSW in the Iceland Basin (−0.0016 ± 0.0002 yr−1). An extrapolation of the observed linear acidification trends suggests that the pH of LSW could drop 0.45 units with respect to pre-industrial levels by the time atmospheric CO2 concentrations reach ~775 ppm. Under circulation conditions and evolution of CO2 emission rates similar to those of the last three decades, by the time atmospheric CO2 reaches 550 ppm, an aragonite undersaturation state could be reached in the cLSW of the Iceland Basin, earlier than surface SPMW.

Late Quaternary palaeo-oceanography of the Denmark Strait overflow pathway, South-East Greenland margin

1998 ◽  
Vol 180 ◽  
pp. 163-167
Author(s):  
Antoon Kuijpers ◽  
Jørn Bo Jensen ◽  
Simon R . Troelstra ◽  
And shipboard scientific party of RV Professor Logachev and RV Dana
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Deep Convection ◽  
Conveyor Belt ◽  
Water Masses ◽  
Labrador Sea ◽  
Greenland Sea ◽  
The North ◽  
Denmark Strait ◽  
The North Atlantic

Direct interaction between the atmosphere and the deep ocean basins takes place today only in the Southern Ocean near the Antarctic continent and in the northern extremity of the North Atlantic Ocean, notably in the Norwegian–Greenland Sea and Labrador Sea. Cooling and evaporation cause surface waters in the latter region to become dense and sink. At depth, further mixing occurs with Arctic water masses from adjacent polar shelves. Export of these water masses from the Norwegian–Greenland Sea (Norwegian Sea Overflow Water) to the North Atlantic basin occurs via two major gateways, the Denmark Strait system and the Faeroe– Shetland Channel and Faeroe Bank Channel system (e.g. Dickson et al. 1990; Fig.1). Deep convection in the Labrador Sea produces intermediate waters (Labrador Sea Water), which spreads across the North Atlantic. Deep waters thus formed in the North Atlantic (North Atlantic Deep Water) constitute an essential component of a global ‘conveyor’ belt extending from the North Atlantic via the Southern and Indian Oceans to the Pacific. Water masses return as a (warm) surface water flow. In the North Atlantic this is the Gulf Stream and the relatively warm and saline North Atlantic Current. Numerous palaeo-oceanographic studies have indicated that climatic changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic Deep Water. Abrupt shut-down of the ocean-overturning and subsequently of the conveyor belt is believed to represent a potential explanation for rapid climate deterioration at high latitudes, such as those that caused the Quaternary ice ages. Here it should be noted, that significant changes in deep convection in Greenland waters have also recently occurred. While in the Greenland Sea deep water formation over the last decade has drastically decreased, a strong increase of deep convection has simultaneously been observed in the Labrador Sea (Sy et al. 1997).

scholarly journals Water mass distributions and transports for the 2014 GEOVIDE cruise in the North Atlantic

2018 ◽  
Vol 15 (7) ◽  
pp. 2075-2090 ◽  
Author(s):  
Maribel I. García-Ibáñez ◽  
Fiz F. Pérez ◽  
Pascale Lherminier ◽  
Patricia Zunino ◽  
Herlé Mercier ◽  
...  
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Water Levels ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
Labrador Sea ◽  
Intermediate Water ◽  
North East ◽  
The North ◽  
The North Atlantic

Abstract. We present the distribution of water masses along the GEOTRACES-GA01 section during the GEOVIDE cruise, which crossed the subpolar North Atlantic Ocean and the Labrador Sea in the summer of 2014. The water mass structure resulting from an extended optimum multiparameter (eOMP) analysis provides the framework for interpreting the observed distributions of trace elements and their isotopes. Central Waters and Subpolar Mode Waters (SPMW) dominated the upper part of the GEOTRACES-GA01 section. At intermediate depths, the dominant water mass was Labrador Sea Water, while the deep parts of the section were filled by Iceland–Scotland Overflow Water (ISOW) and North-East Atlantic Deep Water. We also evaluate the water mass volume transports across the 2014 OVIDE line (Portugal to Greenland section) by combining the water mass fractions resulting from the eOMP analysis with the absolute geostrophic velocity field estimated through a box inverse model. This allowed us to assess the relative contribution of each water mass to the transport across the section. Finally, we discuss the changes in the distribution and transport of water masses between the 2014 OVIDE line and the 2002–2010 mean state. At the upper and intermediate water levels, colder end-members of the water masses replaced the warmer ones in 2014 with respect to 2002–2010, in agreement with the long-term cooling of the North Atlantic Subpolar Gyre that started in the mid-2000s. Below 2000 dbar, ISOW increased its contribution in 2014 with respect to 2002–2010, with the increase being consistent with other estimates of ISOW transports along 58–59° N. We also observed an increase in SPMW in the East Greenland Irminger Current in 2014 with respect to 2002–2010, which supports the recent deep convection events in the Irminger Sea. From the assessment of the relative water mass contribution to the Atlantic Meridional Overturning Circulation (AMOC) across the OVIDE line, we conclude that the larger AMOC intensity in 2014 compared to the 2002–2010 mean was related to both the increase in the northward transport of Central Waters in the AMOC upper limb and to the increase in the southward flow of Irminger Basin SPMW and ISOW in the AMOC lower limb.

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 Trends of anthropogenic CO<sub>2</sub> storage in North Atlantic water masses

2010 ◽  
Vol 7 (5) ◽  
pp. 1789-1807 ◽  
Author(s):  
F. F. Pérez ◽  
M. Vázquez-Rodríguez ◽  
H. Mercier ◽  
A. Velo ◽  
P. Lherminier ◽  
...  
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Atlantic Water ◽  
Average Concentration ◽  
Rate Of Change ◽  
Point Of View ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
The North ◽  
The North Atlantic

Abstract. A high-quality inorganic carbon system database, spanning over three decades (1981–2006) and comprising of 13 cruises, has allowed the applying of the φC°T method and coming up with estimates of the anthropogenic CO2 (Cant) stored in the main water masses of the North Atlantic. In the studied region, strong convective processes convey surface properties, like Cant, into deeper ocean layers and grants this region an added oceanographic interest from the point of view of air-sea CO2 exchanges. Generally, a tendency for decreasing Cant storage rates towards the deep layers has been observed. In the Iberian Basin, the North Atlantic Deep Water has low Cant concentrations and negligible storage rates, while the North Atlantic Central Water in the upper layers shows the largest Cant values and the largest annual increase of its average concentration (1.13 ± 0.14 μmol kg−1 yr−1). This unmatched rate of change in the Cant concentration of the warm upper limb of the Meridional Overturning Circulation decreases towards the Irminger basin (0.68 ± 0.06 μmol kg−1 yr−1) due to the lowering of the buffering capacity. The mid and deep waters in the Irminger Sea show rather similar Cant concentration rates of increase (between 0.33 and 0.45 μmol kg−1 yr−1), whereas in the Iceland basin these layers seem to have been less affected by Cant. Overall, the Cant storage rates in the North Atlantic subpolar gyre during the first half of the 1990s, when a high North Atlantic Oscillation (NAO) phase was dominant, are ~48% higher than during the 1997–2006 low NAO phase that followed. This result suggests that a net decrease in the strength of the North Atlantic sink of atmospheric CO2 has taken place during the present decade. The changes in deep-water ventilation are the main driving processes causing this weakening of the North Atlantic CO2 sink.

scholarly journals Geological and hydrological studies in the Northern Atlantic in 2017 on a section at N59°30’ (68th сruise of the research vessel Akademik Mstislav Keldysh)

2019 ◽  
Vol 59 (1) ◽  
pp. 177-180 ◽  
Author(s):  
A. A. Klyuvitkin ◽  
S. V. Gladyshev ◽  
M. D. Kravchishina ◽  
A. N. Novigatsky ◽  
D. V. Eroshenko ◽  
...  
Keyword(s):  
North Atlantic ◽  
Atmospheric Aerosols ◽  
Deep Convection ◽  
Sediment Traps ◽  
North Atlantic Current ◽  
The North ◽  
Iceland Basin ◽  
East Greenland Current ◽  
Irminger Sea ◽  
The North Atlantic

The first results of the multidisciplinary expedition aboard the RV «Akademik Mstislav Keldysh» to the North Atlantic in July 2017 are given. Continuation of deep convection in the Irminger Sea to a depth of 1500 m, which began in 2015, is discovered. New information is provided on the structure of the main jets of the North Atlantic Current in the Iceland basin and in the Irminger Sea (Irminger Current), as well as the East Greenland Current. New samples of atmospheric aerosols, suspended particulate matter and bottom sediments are collected. New data on the particle fluxes have been obtained using sediment traps.

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

2020 ◽  
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, on the one hand the northward flowing North Atlantic Drift, a Gulf Stream offspring, on the other hand southward moving cold low salinity Polar and Arctic Waters with signatures from Arctic freshwater sources. We have studied by observations, 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 mol C m−2 yr−1 and −4.4 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 and Arctic Water persistent undersaturation and CO2 influx to the excess alkalinity derived from Arctic sources, particularly the Arctic rivers. Carbonate chemistry equilibrium calculations indicate clearly that the excess alkalinity may support a significant portion of the North Atlantic CO2 sink. The Arctic contribution to the North Atlantic CO2 sink which we reveal is previously unrecognized. However, we point out that there are gaps and conflicts in the knowledge about the Arctic alkalinity budget and that future trends in the North Atlantic CO2 sink are connected to developments in the rapidly warming Arctic. The results we present need to be taken into consideration for the question: Will the North Atlantic continue to absorb CO2 in the future as it has in the past?

scholarly journals Trends of anthropogenic CO<sub>2</sub> storage in North Atlantic water masses

2010 ◽  
Vol 7 (1) ◽  
pp. 165-202
Author(s):  
F. F. Pérez ◽  
M. Vázquez-Rodríguez ◽  
H. Mercier ◽  
A. Velo ◽  
P. Lherminier ◽  
...  
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Atlantic Water ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
Oscillation Phase ◽  
Study Region ◽  
The North ◽  
Deep Waters ◽  
The North Atlantic

Abstract. A high-quality inorganic carbon system database spanning over three decades (1981–2006) and comprising 13 cruises has allowed applying the φCT° method and coming up with accurate estimates of the anthropogenic CO2 (Cant) stored in the main water masses of the North Atlantic. In the studied region, strong convective processes convey surface properties, like Cant, into deeper ocean layers and confer this region an added oceanographic interest from the point of view of air-sea CO2 exchanges. Commonly, a tendency for decreasing Cant storage rates towards the deep layers has been observed. In the Iberian Basin, the deep waters (North Atlantic Deep Water) have low Cant values and negligible Cant storage rates, while the North Atlantic Central Water in the upper layers shows the largest Cant concentrations and capacity to increase its storage on a yearly basis (1.13±0.14 μmol kg−1 yr−1). This unmatched Cant storage capacity of the warm upper limb of the Meridional Overturning Circulation weakens towards the Irminger basin (0.68±0.06 μmol kg−1 yr−1) due to the lowering of the buffering capacity. The mid and deep waters in the Irminger Sea show rather homogeneous Cant storage rates (between 0.33 and 0.45 μmol kg−1 yr−1), whereas in the Iceland basin these layers seem to have been less affected by Cant. The Cant storage rates in the study region during the 1991–1997 high NAO (North Atlantic Oscillation) phase are ~48% higher than during the 1997–2006 low NAO phase that followed. This result suggests that a net decrease in the strength of the North Atlantic sink of atmospheric CO2has taken place during the present decade. The changes in deep-water ventilation together with a detrimental renewal of the main water masses are likely the main driving processes causing this weakening of the North Atlantic CO2sink.

Arctic vs. North Atlantic water mass exchanges in Fram Strait from Pb isotopes in sedimentsThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network.

2008 ◽  
Vol 45 (11) ◽  
pp. 1253-1263 ◽  
Author(s):  
Jean Carignan ◽  
Claude Hillaire-Marcel ◽  
Anne de Vernal
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
North Atlantic Ocean ◽  
Atlantic Water ◽  
The Arctic ◽  
Fram Strait ◽  
The North ◽  
Anthropogenic Inputs ◽  
North Atlantic Water ◽  
The North Atlantic

Surface sediment samples (n = 10), collected between Spitzbergen and Greenland, and two cores raised east (C04) and west (C16) from Fram Strait were analyzed for their chemical and isotopic (Pb) compositions to trace the source of sediments and water masses exchanging between the Arctic and the North Atlantic oceans. In surface sediments, variable major and trace element concentrations suggest variations in both the mineralogy (carbonate and quartz dilution of other silicate minerals) and source regions of detrital supplies, based on Th/Zr and, to a lesser extent, on Th/U ratios. Each core site shows specific but nearly constant Th/Zr ratios, indicating homogeneous source supplies. At both core sites, Pb concentrations and isotopic compositions display similar patterns: homogeneous low Pb and radiogenic crustal signals below 5–10 cm, contrasting with high Pb and less radiogenic anthropogenic inputs at core-tops. However, the differing pre-anthropogenic Pb isotopic ratios in C04 and C16 confirm the involvement of distinct source supplies east and west of Fram Strait. We suggest that this isotopic specificity is mainly owing to inputs of material carried from northwestern Europe by the North Atlantic water mass and from the Laptev Sea by the Transpolar Drift, respectively. Some material from the Greenland margin and possibly from the North Atlantic Ocean may reach this zone as well. Sediments from the western Arctic are not significantly transported into the Fram Strait area, suggesting that the Canadian and the Eurasian basins remained decoupled, at least during the time span of the cored sediments (∼2000 years).

scholarly journals Change in the North Atlantic circulation associated with the mid-Pleistocene transition

2018 ◽  
Vol 14 (11) ◽  
pp. 1639-1651 ◽  
Author(s):  
Gloria M. Martin-Garcia ◽  
Francisco J. Sierro ◽  
José A. Flores ◽  
Fátima Abrantes
Keyword(s):  
North Atlantic ◽  
Major Change ◽  
Water Masses ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
North Atlantic Current ◽  
The North ◽  
Oceanic Fronts ◽  
Surface Circulation ◽  
The North Atlantic

Abstract. The southwestern Iberian margin is highly sensitive to changes in the distribution of North Atlantic currents and to the position of oceanic fronts. In this work, the evolution of oceanographic parameters from 812 to 530 ka (MIS20–MIS14) is studied based on the analysis of planktonic foraminifer assemblages from site IODP-U1385 (37∘34.285′ N, 10∘7.562′ W; 2585 m b.s.l.). By comparing the obtained results with published records from other North Atlantic sites between 41 and 55∘ N, basin-wide paleoceanographic conditions are reconstructed. Variations of assemblages dwelling in different water masses indicate a major change in the general North Atlantic circulation during MIS16, coinciding with the definite establishment of the 100 ky cyclicity associated with the mid-Pleistocene transition. At the surface, this change consisted in the redistribution of water masses, with the subsequent thermal variation, and occurred linked to the northwestward migration of the Arctic Front (AF), and the increase in the North Atlantic Deep Water (NADW) formation with respect to previous glacials. During glacials prior to MIS16, the NADW formation was very weak, which drastically slowed down the surface circulation; the AF was at a southerly position and the North Atlantic Current (NAC) diverted southeastwards, developing steep south–north, and east–west, thermal gradients and blocking the arrival of warm water, with associated moisture, to high latitudes. During MIS16, the increase in the meridional overturning circulation, in combination with the northwestward AF shift, allowed the arrival of the NAC to subpolar latitudes, multiplying the moisture availability for ice-sheet growth, which could have worked as a positive feedback to prolong the glacials towards 100 ky cycles.

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