scholarly journals The impact of the wind stress curl in the North Atlantic on the Atlantic inflow to the Norwegian Sea toward the Arctic

2003 ◽  
Vol 30 (17) ◽  
pp. n/a-n/a ◽  
Author(s):  
Kjell Arild Orvik ◽  
Øystein Skagseth
Keyword(s):  
Wind Stress ◽  
North Atlantic ◽  
The Arctic ◽  
Wind Stress Curl ◽  
Norwegian Sea ◽  
The North ◽  
The North Atlantic ◽  
The Impact

scholarly journals Transport and Fate of 137Cs Released From Multiple Sources in the North Atlantic and Arctic Oceans

2021 ◽  
Vol 8 ◽  
Author(s):  
Vladimir Maderich ◽  
Kyeong Ok Kim ◽  
Roman Bezhenar ◽  
Kyung Tae Jung ◽  
Vazira Martazinova ◽  
...  
Keyword(s):  
Bottom Sediment ◽  
North Atlantic ◽  
River Runoff ◽  
Global Fallout ◽  
The Arctic ◽  
Multiple Sources ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
Secondary Contamination

The North Atlantic and Arctic oceans, along with the North Pacific, are the main reservoirs of anthropogenic radionuclides introduced in the past 75 years. The POSEIDON-R compartment model was applied to the North Atlantic and Arctic oceans to reconstruct 137Cs contamination in 1945–2020 due to multiple sources: global fallout, exchange flows with other oceans, point-source inputs in the ocean from reprocessing plants and other nuclear facilities, the impact of the Chernobyl accident and secondary contamination resulting from river runoff and redissolution from bottom sediments. The model simulated the marine environment as a system of 3D compartments comprising the water column, bottom sediment, and biota. The dynamic model described the transfer of 137Cs through the pelagic and benthic food chains. The simulation results were validated using the marine database MARIS. The calculated concentrations of 137Cs in the seaweed and non-piscivorous and piscivorous pelagic fish mostly followed the concentration of 137Cs in water. The concentration in coastal predator fish lagged behind the concentration in water as a result of a diet that includes both pelagic and benthic organisms. The impact of each considered source on the total concentration of 137Cs in non-piscivorous fish in the regions of interest was analyzed. Whereas the contribution from global fallout dominated in 1960–1970, in 1970–1990, the contribution of 137Cs released from reprocessing plants exceeded the contributions from other sources in almost all considered regions. Secondary contamination due to river runoff was less than 4% of ocean influx. The maximum total inventory of 137Cs in the Arctic Ocean (31,122 TBq) was reached in 1988, whereas the corresponding inventory in the bottom sediment was approximately 6% of the total. The general agreement between simulated and observed 137Cs concentrations in water and bottom sediment was confirmed by the estimates of geometric mean and geometric standard deviation, which varied from 0.89 to 1.29 and from 1.22 to 1.87, respectively. The approach used is useful to synthesize measurement and simulation data in areas with observational gaps. For this purpose, 13 representative regions in the North Atlantic and Arctic oceans were selected for monitoring by using the “etalon” method for classification.

scholarly journals The Wintertime Wind Stress Curl Field in the North Atlantic and Its Relation to Atmospheric Teleconnection Patterns

2010 ◽  
Vol 67 (5) ◽  
pp. 1687-1694 ◽  
Author(s):  
Shusaku Sugimoto ◽  
Kimio Hanawa
Keyword(s):  
Wind Stress ◽  
North Atlantic ◽  
Wind Stress Curl ◽  
Atlantic Sector ◽  
Atmospheric Teleconnection ◽  
Maximum Covariance Analysis ◽  
Teleconnection Patterns ◽  
The North ◽  
The North Atlantic ◽  
Atmospheric Teleconnection Patterns

Abstract Adopting a rotated empirical orthogonal function (REOF) analysis and a maximum covariance analysis (MCA), characteristics of the wintertime wind stress curl (WSC) anomaly field in the North Atlantic are investigated. In terms of both temporal variation and spatial distribution, the first four leading modes of WSC show a one-to-one relation with four atmospheric teleconnection patterns over the North Atlantic sector: the North Atlantic Oscillation (NAO) and the east Atlantic (EA), tropical–Northern Hemisphere (TNH), and Pacific–North American (PNA) patterns. These four patterns characterize the WSC variations over the different regions in the North Atlantic: NAO and EA over the eastern side of the basin, TNH over the central part of the basin, and PNA over the western side of the basin.

scholarly journals Impact of data assimilation of physical variables on the spring bloom from TOPAZ operational runs in the North Atlantic

Ocean Science ◽  
2009 ◽  
Vol 5 (4) ◽  
pp. 635-647 ◽  
Author(s):  
A. Samuelsen ◽  
L. Bertino ◽  
C. Hansen
Keyword(s):  
Data Assimilation ◽  
North Atlantic ◽  
Spring Bloom ◽  
Ecosystem Model ◽  
Ocean Model ◽  
Sea Surface ◽  
The Arctic ◽  
The North ◽  
The North Atlantic ◽  
The Impact

Abstract. A reanalysis of the North Atlantic spring bloom in 2007 was produced using the real-time analysis from the TOPAZ North Atlantic and Arctic forecasting system. The TOPAZ system uses a hybrid coordinate general circulation ocean model and assimilates physical observations: sea surface anomalies, sea surface temperatures, and sea-ice concentrations using the Ensemble Kalman Filter. This ocean model was coupled to an ecosystem model, NORWECOM (Norwegian Ecological Model System), and the TOPAZ-NORWECOM coupled model was run throughout the spring and summer of 2007. The ecosystem model was run online, restarting from analyzed physical fields (result after data assimilation) every 7 days. Biological variables were not assimilated in the model. The main purpose of the study was to investigate the impact of physical data assimilation on the ecosystem model. This was determined by comparing the results to those from a model without assimilation of physical data. The regions of focus are the North Atlantic and the Arctic Ocean. Assimilation of physical variables does not affect the results from the ecosystem model significantly. The differences between the weekly mean values of chlorophyll are normally within 5–10% during the summer months, and the maximum difference of ~20% occurs in the Arctic, also during summer. Special attention was paid to the nutrient input from the North Atlantic to the Nordic Seas and the impact of ice-assimilation on the ecosystem. The ice-assimilation increased the phytoplankton concentration: because there was less ice in the assimilation run, this increased both the mixing of nutrients during winter and the area where production could occur during summer. The forecast was also compared to remotely sensed chlorophyll, climatological nutrients, and in-situ data. The results show that the model reproduces a realistic annual cycle, but the chlorophyll concentrations tend to be between 0.1 and 1.0 mg chla/m3 too low during winter and spring and 1–2 mg chla/m3 too high during summer. Surface nutrients on the other hand are generally lower than the climatology throughout the year.

scholarly journals Stochastic Forcing of the North Atlantic Wind-Driven Ocean Circulation. Part II: An Analysis of the Dynamical Ocean Response Using Generalized Stability Theory

2006 ◽  
Vol 36 (3) ◽  
pp. 316-334 ◽  
Author(s):  
Kettyah C. Chhak ◽  
Andrew M. Moore ◽  
Ralph F. Milliff ◽  
Grant Branstator ◽  
William R. Holland ◽  
...  
Keyword(s):  
Wind Stress ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Boundary Region ◽  
Western Boundary ◽  
Transient Growth ◽  
Wind Stress Curl ◽  
Stochastic Forcing ◽  
The North ◽  
The North Atlantic

Abstract As discussed in Part I of this study, the magnitude of the stochastic component of wind stress forcing is comparable to that of the seasonal cycle and thus will likely have a significant influence on the ocean circulation. By forcing a quasigeostrophic model of the North Atlantic Ocean circulation with stochastic wind stress curl data from the NCAR CCM3, it was found in Part I that much of the stochastically induced variability in the ocean circulation is confined to the western boundary region and some major topographic features even though the stochastic forcing is basinwide. This can be attributed to effects of bathymetry and vorticity gradients in the basic state on the system eigenmodes. Using generalized stability theory (GST), it was found in Part I that transient growth due to the linear interference of nonnormal eigenmodes enhances the stochastically induced variance. In the present study, the GST analysis of Part I is extended and it is found that the patterns of wind stress curl that are most effective for inducing variability in the model have their largest projection on the most nonnormal eigenmodes of the system. These eigenmodes are confined primarily to the western boundary region and are composed of long Rossby wave packets that are Doppler shifted by the Gulf Stream to have eastward group velocity. Linear interference of these eigenmodes yields transient growth of stochastically induced perturbations, and it is this process that maintains the variance of the stochastically induced circulations. Analysis of the large-scale circulation also reveals that the system possesses a large number of degrees of freedom, which has significant implications for ocean prediction. Sensitivity studies show that the results and conclusions of this study are insensitive and robust to variations in model parameters and model configuration.

Polar Climate Instability and Climate Teleconnections from the Arctic to the Midlatitudes and Tropics

2009 ◽  
Vol 22 (13) ◽  
pp. 3513-3539 ◽  
Author(s):  
Guido Vettoretti ◽  
Marc d’Orgeville ◽  
William R. Peltier ◽  
Marek Stastna
Keyword(s):  
North Atlantic ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Overturning Circulation ◽  
Polar Climate ◽  
Enso Events ◽  
The North ◽  
The North Atlantic ◽  
The Tropics ◽  
The Impact

Abstract It is generally accepted that the ocean thermohaline circulation plays a key role in polar climate stability and rapid climate change. Recently reported analyses of the impact of anomalous freshwater outflows from the North American continent onto either the North Atlantic or Arctic Oceans demonstrate that, in either case, a clear reduction in the Atlantic meridional overturning circulation, accompanied by an increase in sea ice extent, is predicted. The results also reconcile proxy-inferred Younger Dryas Greenland temperature variations. The aim of the present work is to provide a detailed investigation of the pathways along which the signal associated with overturning circulation anomalies propagates into both the midlatitudes and the tropics and the effect such teleconnections have on the tropical ocean–atmosphere system. The authors consider both the impact of substantial slowing of the overturning circulation due to freshwater forcing of the North Atlantic as well as its recovery after the anomalous forcing has ceased. The changes in tropical climate variability are shown to manifest themselves in shifts of both the typical time scale and intensity of ENSO events in the model. Evidence is presented for mechanisms that involve both atmospheric and oceanic pathways through which such Northern Hemisphere high-latitude events are communicated into both the midlatitudes and the tropics and thereafter transformed into changes in the nature of tropical variability.

scholarly journals Eddy permitting simulations of freshwater injection from major Northern Hemisphere outlets during the last deglacial

2021 ◽  
Author(s):  
Ryan Love ◽  
Heather Andres ◽  
Alan Condron ◽  
Lev Tarasov
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Critical Role ◽  
The Arctic ◽  
Bering Strait ◽  
The North ◽  
Glacial Runoff ◽  
The North Atlantic ◽  
The Impact ◽  
Climate Transitions

Abstract. Freshwater, in the form of glacial runoff, is hypothesized to play a critical role in centennial to millennial scale climate variability such as the Younger Dryas and Dansgaard-Oeschger Events. Indeed, freshwater injection/hosing experiments with climate models have long shown that freshwater has the capability of generating such abrupt climate transitions. However, the relationship between freshwater and abrupt climate transitions is not straightforward. Large-scale glacial runoff events, such as Meltwater Pulse 1A, are not always temporally proximal to subsequent large-scale cooling. As well, the typical design of hosing experiments tends to artificially amplify the climate response. This study explores the impact that limitations in the representation of runoff in conventional hosing simulations has on our understanding of this relationship and addresses the more fundamental question of where coastally released freshwater is transported when it reaches the ocean. We focus particularly on the prior use of excessive freshwater volumes (often by a factor of 5) and present-day (rather than paleo) ocean gateways, as well as the injection of freshwater directly over sites of deep-water formation (DWF) rather than at runoff locations. We track the routing of glaciologically-constrained freshwater volumes from four different plausible injection locations in a suite of eddy-permitting glacial ocean simulations using MITGCM under both open and closed Bering Strait conditions. Restricting freshwater forcing values to realistic ranges results in less spreading of freshwater across the North Atlantic and indicates that the response of DWF depends strongly on the geographical location of meltwater input. In particular, freshwater released into the Gulf of Mexico has little impact on DWF regions as a result of turbulent mixing by the Gulf Stream. In contrast, freshwater released from the Eurasian Ice sheet or initially into the Arctic is found to have the largest impact on DWF in the North Atlantic and GIN seas. Additional experiments show that when the Bering Strait is open, much like present-day, the Mackenzie River source exhibits twice as much freshening of the Labrador sea as a closed Bering Strait. Finally, our results illustrate that applying a freshwater hosing directly into the North Atlantic with even realistic freshwater amounts still over-estimates the effect of terrestrial runoff on ocean circulation.

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.

Sign in / Sign up

Export Citation Format

Share Document