scholarly journals Effect of gas-transfer-velocity parameterization choice on CO<sub>2</sub> air–sea fluxes in the North Atlantic and European Arctic

2015 ◽  
Vol 12 (6) ◽  
pp. 2591-2616
Author(s):  
I. Wróbel ◽  
J. Piskozub
Keyword(s):  
North Atlantic ◽  
World Ocean ◽  
Software Tool ◽  
The Arctic ◽  
Gas Transfer ◽  
Transfer Velocity ◽  
Gas Transfer Velocity ◽  
The North ◽  
European Arctic ◽  
The North Atlantic

Abstract. The ocean sink is an important part of the anthropogenic CO2 budget. Because the terrestrial biosphere is usually treated as a residual, understanding the uncertainties the net flux into the ocean sink is crucial for understanding the global carbon cycle. One of the sources of uncertainty is the parameterization of CO2 gas transfer velocity. We used a recently developed software tool, FluxEngine, to calculate monthly net carbon air–sea flux for the extratropical North Atlantic, European Arctic as well as global values (or comparison) using several available parameterizations of gas transfer velocity of different dependence of wind speed, both quadratic and cubic. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic, a large sink of CO2 and a region with good measurement coverage, characterized by strong winds. We show that this uncertainty is smaller in the North Atlantic and in the Arctic than globally, within 5 % in the North Atlantic and 4 % in the European Arctic, comparing to 9 % for the World Ocean when restricted to functions with quadratic wind dependence and respectively 42, 40 and 67 % for all studied parameterizations. We propose an explanation of this smaller uncertainty due to the combination of higher than global average wind speeds in the North Atlantic and lack of seasonal changes in the flux direction in most of the region. We also compare the available pCO2 climatologies (Takahashi and SOCAT) pCO2 discrepancy in annual flux values of 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal flux changes in the Arctic have inverse seasonal change in both climatologies, caused most probably by insufficient data coverage, especially in winter.

scholarly journals Effect of gas-transfer velocity parameterization choice on air–sea CO<sub>2</sub> fluxes in the North Atlantic Ocean and the European Arctic

Ocean Science ◽  
2016 ◽  
Vol 12 (5) ◽  
pp. 1091-1103 ◽  
Author(s):  
Iwona Wrobel ◽  
Jacek Piskozub
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Global Ocean ◽  
Gas Transfer ◽  
Data Sets ◽  
Transfer Velocity ◽  
The North ◽  
European Arctic ◽  
The North Atlantic

Abstract. The oceanic sink of carbon dioxide (CO2) is an important part of the global carbon budget. Understanding uncertainties in the calculation of this net flux into the ocean is crucial for climate research. One of the sources of the uncertainty within this calculation is the parameterization chosen for the CO2 gas-transfer velocity. We used a recently developed software toolbox, called the FluxEngine (Shutler et al., 2016), to estimate the monthly air–sea CO2 fluxes for the extratropical North Atlantic Ocean, including the European Arctic, and for the global ocean using several published quadratic and cubic wind speed parameterizations of the gas-transfer velocity. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic Ocean. This region is a large oceanic sink of CO2, and it is also a region characterized by strong winds, especially in winter but with good in situ data coverage. We show that the uncertainty in the parameterization is smaller in the North Atlantic Ocean and the Arctic than in the global ocean. It is as little as 5 % in the North Atlantic and 4 % in the European Arctic, in comparison to 9 % for the global ocean when restricted to parameterizations with quadratic wind dependence. This uncertainty becomes 46, 44, and 65 %, respectively, when all parameterizations are considered. We suggest that this smaller uncertainty (5 and 4 %) is caused by a combination of higher than global average wind speeds in the North Atlantic (> 7 ms−1) and lack of any seasonal changes in the direction of the flux direction within most of the region. We also compare the impact of using two different in situ pCO2 data sets (Takahashi et al. (2009) and Surface Ocean CO2 Atlas (SOCAT) v1.5 and v2.0, for the flux calculation. The annual fluxes using the two data sets differ by 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal fluxes in the Arctic computed from the two data sets disagree with each other possibly due to insufficient spatial and temporal data coverage, especially in winter.

scholarly journals Air-sea momentum flux climatologies: A review of drag relation for parameterization choice on wind stress in the North Atlantic and the European Arctic

2018 ◽  
Author(s):  
Iwona Wrobel-Niedzwiecka ◽  
Violetta Drozdowska ◽  
Jacek Piskozub
Keyword(s):  
Wind Speed ◽  
Drag Coefficient ◽  
Wind Stress ◽  
North Atlantic ◽  
Momentum Flux ◽  
The Arctic ◽  
The North ◽  
European Arctic ◽  
The North Atlantic ◽  
The Tropics

Abstract. In this paper we have chosen to check the differences between the relevant or most commonly used parameterizations for drag coefficient (CD) for the momentum transfer values, especially in the North Atlantic (NA) and the European Arctic (EA). As is well know, the exact equation in the North equation that describes the connection betwenn the drag coefficient and wind speed depends on the author. We studied monthly values of air-sea momentum flux resulting from the choice of different drag coefficient parameterizations, adapted them to momentum flux (wind stress) calculations using SAR wind fields, sea-ice masks, as well as integrating procedures. We calculated monthly momentum flux averages on a 1º x 1º degree grid and derive average values for the North Atlantic and the European Arctic. We compared the resulting spreads in momentum flux to global values and values in the tropics, an area of prevailing low winds. We show that the choice of drag coefficient parameterization can lead to significant differences in resultant momentum flux (or wind stress) values. We found that the spread of results stemming from the choice of drag coefficient parameterization was 14 % in the Arctic, the North Atlantic and globally, but it was higher (19 %) in the tropics. On monthly time scales, the differences were larger at up to 29 % in the North Atlantic and 36 % in the European Arctic (in months of low winds) and even 50 % locally (the area west of Spitsbergen). When we chose the oldest parameterization (e.g Wu, 1969 (W69)) values of momentum flux were largest for all months, in compare to values from the two newest parameterizations (Large and Yeager, 2004 (LY04) and Andreas, 2012 (A12)), in both regions with high and low winds and CD values were consistently higher for all wind speeds. For global data not much seasonal change was note due to the fact that the strongest winds are in autumn and winter as these seasons are inverse by six months for the northern and southern hemispheres. The situation was more complicated when we considered results from the North Atlantic, as the seasonal variation in wind speed is clearly marked out there. With high winter winds, the A12 parameterization was no longer the one that produces the smallest wind stress. In this region, in summer, the highest wind stress values were produced by the NCEP/NCAR reanalysis, where in CD has a constant value. However, for low summer winds, it is the lowermost outlier. As the A12 parameterization behaves so distinctly differently with low winds, we showed seasonal results for the tropical ocean. The sequence of values for the parameterization was similar to that of the global ocean, but with visible differences betwenn NCEP/NCAR, A12 and LY04 parameterizaions. Because parameterization is supported with the largest experimental data set observations of very low (or even negative) momentum flux values for developed swell and low winds, our results suggest that most circulation models overestimate momentum flux.

scholarly journals Halocline Catastrophes, Sea Ice, and Ocean Climate

1990 ◽  
Vol 14 ◽  
pp. 328-328 ◽  
Author(s):  
Knut Aagaard
Keyword(s):  
Sea Ice ◽  
Fresh Water ◽  
North Atlantic ◽  
World Ocean ◽  
Deep Ocean ◽  
Present Situation ◽  
The Arctic ◽  
The North ◽  
The Arctic Ocean ◽  
The North Atlantic

Rapid melting of continental ice during deglaciations has been hypothesized to shift the thermohaline circulation of the world ocean to a mode radically different from the one dominated by the North Atlantic, such as operates today. This scenario has been referred to as the halocline catastrophe. We consider here the freezing, transport, and melting of sea ice in the North Atlantic sector as a possible modern analog to such events.The rejection of salt during the freezing and subsequent development of sea ice results, by early summer, in ice with only 5–10% of its original salt content. Since sea ice several meters thick is typically formed annually in the polar regions, the distillation rates from freezing are fully comparable to those from evaporation in such highly evaporative basins as the Red Sea. If the ice is subsequently exported from its production area, then freezing and melting are the oceanic equivalent of the hydrologic cycle. In the Arctic, the major ice outflow from the 107 km2 of the Polar Basin occurs east of Greenland, where the exodus represents a fresh-water transport of at least 2800 km3 a−1. This is a discharge more than twice that of North America’s four largest rivers combined.The fresh water can subsequently be traced around the subpolar gyre of the North Atlantic, on its way transferring small but significant amounts of buoyancy into the interior convective gyres, e.g. in the Greenland Sea. The convection which occurs in these gyres under present climatic conditions makes them major ventilation and water mass formation sites for the deep world ocean, but because the density of sea water at constant pressure and low temperature is almost solely dependent on salinity, the convection is extremely sensitive to changes in the freshwater supply to the gyres. Small variations in the supply will be transferred into the deep ocean by convection, where they will be manifested by a cooling and freshening, such as has recently been observed in the deep North Atlantic. However, if the surface layers are freshened too much, cooling even to the freezing point will be insufficient to initiate convection. Instead, the convective gyres will be capped by a fresh-water lid, essentially what has been proposed in the halocline catastrophe scenarios. During such events, sea ice will form in the gyres, sometimes with disastrous consequences, as occurred north of Iceland during the late 1960s when, during the extreme years of 1965 and 1968, the entire north and east coasts of Iceland were enveloped by sea ice; at the same time, renewal to the north of the deep ocean waters diminished or ceased.We suggest that the present-day Greenland and Iceland seas, and probably also the Labrador Sea, are rather delicately poised with respect to their ability to sustain convection, and that we have in fact during the past several decades seen a small-scale analog to the halocline catastrophe proposed for past deglaciations. A major difference is that the present situation does not require dramatic increases in fresh-water flux to effect a capping of the convection; nor does it depend on deglaciation. Rather, very modest changes in the disposition of the fresh water presently carried by the East Greenland Current can alter or stop the convection; and the principal source of fresh water is sea ice, rather than glacial ice. The essence of the present situation is that the large fresh-water output from the Arctic Ocean, which is the distillate of freezing, passes perilously close to the very weakly stratified convective gyres; and that the stratification in these gyres is easily perturbed, either by variations in the discharge from the Arctic Ocean or by leaks or recirculation from the boundary current.

scholarly journals Halocline Catastrophes, Sea Ice, and Ocean Climate

1990 ◽  
Vol 14 ◽  
pp. 328
Author(s):  
Knut Aagaard
Keyword(s):  
Sea Ice ◽  
Fresh Water ◽  
North Atlantic ◽  
World Ocean ◽  
Deep Ocean ◽  
Present Situation ◽  
The Arctic ◽  
The North ◽  
The Arctic Ocean ◽  
The North Atlantic

Rapid melting of continental ice during deglaciations has been hypothesized to shift the thermohaline circulation of the world ocean to a mode radically different from the one dominated by the North Atlantic, such as operates today. This scenario has been referred to as the halocline catastrophe. We consider here the freezing, transport, and melting of sea ice in the North Atlantic sector as a possible modern analog to such events. The rejection of salt during the freezing and subsequent development of sea ice results, by early summer, in ice with only 5–10% of its original salt content. Since sea ice several meters thick is typically formed annually in the polar regions, the distillation rates from freezing are fully comparable to those from evaporation in such highly evaporative basins as the Red Sea. If the ice is subsequently exported from its production area, then freezing and melting are the oceanic equivalent of the hydrologic cycle. In the Arctic, the major ice outflow from the 107 km2 of the Polar Basin occurs east of Greenland, where the exodus represents a fresh-water transport of at least 2800 km3 a−1. This is a discharge more than twice that of North America’s four largest rivers combined. The fresh water can subsequently be traced around the subpolar gyre of the North Atlantic, on its way transferring small but significant amounts of buoyancy into the interior convective gyres, e.g. in the Greenland Sea. The convection which occurs in these gyres under present climatic conditions makes them major ventilation and water mass formation sites for the deep world ocean, but because the density of sea water at constant pressure and low temperature is almost solely dependent on salinity, the convection is extremely sensitive to changes in the freshwater supply to the gyres. Small variations in the supply will be transferred into the deep ocean by convection, where they will be manifested by a cooling and freshening, such as has recently been observed in the deep North Atlantic. However, if the surface layers are freshened too much, cooling even to the freezing point will be insufficient to initiate convection. Instead, the convective gyres will be capped by a fresh-water lid, essentially what has been proposed in the halocline catastrophe scenarios. During such events, sea ice will form in the gyres, sometimes with disastrous consequences, as occurred north of Iceland during the late 1960s when, during the extreme years of 1965 and 1968, the entire north and east coasts of Iceland were enveloped by sea ice; at the same time, renewal to the north of the deep ocean waters diminished or ceased. We suggest that the present-day Greenland and Iceland seas, and probably also the Labrador Sea, are rather delicately poised with respect to their ability to sustain convection, and that we have in fact during the past several decades seen a small-scale analog to the halocline catastrophe proposed for past deglaciations. A major difference is that the present situation does not require dramatic increases in fresh-water flux to effect a capping of the convection; nor does it depend on deglaciation. Rather, very modest changes in the disposition of the fresh water presently carried by the East Greenland Current can alter or stop the convection; and the principal source of fresh water is sea ice, rather than glacial ice. The essence of the present situation is that the large fresh-water output from the Arctic Ocean, which is the distillate of freezing, passes perilously close to the very weakly stratified convective gyres; and that the stratification in these gyres is easily perturbed, either by variations in the discharge from the Arctic Ocean or by leaks or recirculation from the boundary current.

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.

Meridional Tripole Mode of Winter Precipitation over the Arctic and Continental North Africa–Eurasia

2021 ◽  
pp. 1
Author(s):  
Xiaolin Liu ◽  
Jianhua Lu ◽  
Yimin Liu ◽  
Guoxiong Wu
Keyword(s):  
Time Series ◽  
North Africa ◽  
North Atlantic ◽  
Hadley Cell ◽  
The Arctic ◽  
Positive Phase ◽  
The North ◽  
Ferrel Cell ◽  
The North Atlantic ◽  
Westerly Jets

AbstractWintertime precipitation is vital to the growth of glaciers in the northern hemisphere. We find a tripole mode of precipitation (PTM), with each pole of the mode extending zonally over the eastern hemisphere roughly between 30°W and 120°E, and the positive/negative/positive structure for its positive phase extending meridionally from the Arctic to the continental North Africa–Eurasia. The large-scale dynamics associated with the PTM is explored. The positive phase of the PTM is associated with the negative while eastward-shifted phase of the North Atlantic Oscillation (NAO) and a zonal band of positive SST anomaly in the tropics, together with a narrowed Hadley cell and weakened Ferrel cell. While being north-eastward tilted and separated from their North Africa-Eurasia counterpart in the climatological mean, the upper-tropospheric westerly jets over the east Pacific and north Atlantic become extending zonally and shifting southward and hence form a circumpolar subtropical jet as a whole by connecting with the westerly jets over the North Africa-Eurasia. The enhanced zonal winds over the north Atlantic promote more synoptic-scale transient eddies which are waveguided by the jet streams. The polar vortex weakens and cold air dips southward from the North Pole. Further diagnosis of the E-vectors suggests that transient eddies have a positive feedback on the weakening of Ferrel cell. Opposite features are associated with the negative phase of the PTM. The reconstructed time series using multiple linear regression on the NAO index and the tropical SST averaged over 20°S– 20°N, can explain 62.4% of the variance of the original the original precipitation time series.

X. NATO and the Challenge in the North Atlantic and the Arctic

2018 ◽  
Vol 93 (1) ◽  
pp. 121-128 ◽  
Author(s):  
James G Foggo ◽  
Alarik Fritz
Keyword(s):  
North Atlantic ◽  
The Arctic ◽  
The North ◽  
The North Atlantic

scholarly journals Carbon cycling in the Arctic Archipelago: the export of Pacific carbon to the North Atlantic

2009 ◽  
Vol 6 (1) ◽  
pp. 971-994 ◽  
Author(s):  
E. H. Shadwick ◽  
T. Papakyriakou ◽  
A. E. F. Prowe ◽  
D. Leong ◽  
S. A. Moore ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
North Atlantic ◽  
Barents Sea ◽  
Hydrological Cycle ◽  
Dissolved Inorganic Carbon ◽  
The Arctic ◽  
Co2 Uptake ◽  
The North ◽  
The Arctic Ocean ◽  
The North Atlantic

Abstract. The Arctic Ocean is expected to be disproportionately sensitive to climatic changes, and is thought to be an area where such changes might be detected. The Arctic hydrological cycle is influenced by: runoff and precipitation, sea ice formation/melting, and the inflow of saline waters from Bering and Fram Straits and the Barents Sea Shelf. Pacific water is recognizable as intermediate salinity water, with high concentrations of dissolved inorganic carbon (DIC), flowing from the Arctic Ocean to the North Atlantic via the Canadian Arctic Archipelago. We present DIC data from an east-west section through the Archipelago, as part of the Canadian International Polar Year initiatives. The fractions of Pacific and Arctic Ocean waters leaving the Archipelago and entering Baffin Bay, and subsequently the North Atlantic, are computed. The eastward transport of carbon from the Pacific, via the Arctic, to the North Atlantic is estimated. Altered mixing ratios of Pacific and freshwater in the Arctic Ocean have been recorded in recent decades. Any climatically driven alterations in the composition of waters leaving the Arctic Archipelago may have implications for anthropogenic CO2 uptake, and hence ocean acidification, in the subpolar and temperate North Atlantic.

scholarly journals Modeling the climatic implications of the Guliya δ<sup>18</sup>O record during the past 130 ka

2012 ◽  
Vol 8 (3) ◽  
pp. 1885-1914
Author(s):  
D. Xiao ◽  
P. Zhao ◽  
Y. Wang ◽  
X. Zhou
Keyword(s):  
North Atlantic ◽  
Climate Model ◽  
Surface Air Temperature ◽  
Late Summer ◽  
The Arctic ◽  
The Past ◽  
The North ◽  
Precession Cycle ◽  
The North Atlantic ◽  
Anomalous Pattern

Abstract. Using an intermediate-complexity UVic Earth System Climate Model (UVic Model), the geographical and seasonal implications and an indicative sense of the historical climate found in the δ18O record of the Guliya ice core (hereinafter, the Guliya δ18O) are investigated under time-dependent orbital forcing with an acceleration factor of 100 over the past 130 ka. The results reveal that the simulated late-summer (August–September) Guliya surface air temperature (SAT) reproduces the 23-ka precession and 43-ka obliquity cycles in the Guliya δ18O. Furthermore, the Guliya δ18O is significantly correlated with the SAT over the Northern Hemisphere (NH), which suggests the Guliya δ18O is an indicator of the late-summer SAT in the NH. Corresponding to the warm and cold phases of the precession cycle in the Guliya temperature, there are two anomalous patterns in the SAT and sea surface temperature (SST) fields. The first anomalous pattern shows an increase in the SAT (SST) toward the Arctic, possibly associated with the joint effect of the precession and obliquity cycles, and the second anomalous pattern shows an increase in the SAT (SST) toward the equator, possibly due to the influence of the precession cycle. Additionally, the summer (winter) Guliya and NH temperatures are higher (lower) in the warm phases of Guliya late-summer SAT than in the cold phases. Furthermore, the Guliya SAT is closely related to the North Atlantic SST, in which the Guliya precipitation may act as a "bridge" linking the Guliya SAT and the North Atlantic SST.

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