scholarly journals Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products

Ocean Science ◽  
2014 ◽  
Vol 10 (3) ◽  
pp. 523-546 ◽  
Author(s):  
T. S. Dotto ◽  
R. Kerr ◽  
M. M. Mata ◽  
M. Azaneu ◽  
I. Wainer ◽  
...  
Keyword(s):  
Deep Water ◽  
Sea Water ◽  
Horizontal Resolution ◽  
Weddell Sea ◽  
Water Masses ◽  
Ocean Reanalysis ◽  
In Situ Data ◽  
Ocean Data Assimilation ◽  
Sea Bottom ◽  
Warm Deep Water

Abstract. We assessed and evaluated the performance of five ocean reanalysis products in reproducing essential hydrographic properties and their associated temporal variability for the Weddell Sea, Antarctica. The products used in this assessment were ECMWF ORAS4 (European Centre for Medium-Range Weather Forecasts Ocean Reanalysis System 4), CFSR (Climate Forecast System Reanalysis), MyOcean UR025.4 (University of Reading), ECCO2 (Estimating the Circulation and Climate of the Ocean, Phase II) and SODA (Simple Ocean Data Assimilation). The present study focuses on the Weddell Sea deep layer, which is composed of the following three main water masses: Warm Deep Water (WDW), Weddell Sea Deep Water (WSDW) and Weddell Sea Bottom Water (WSBW). The MyOcean UR025.4 product provided the most accurate representation of the structure and thermohaline properties of the Weddell Sea water masses when compared with observations. All the ocean reanalysis products analyzed exhibited limited capabilities in representing the surface water masses in the Weddell Sea. The CFSR and ECCO2 products were not able to represent deep water masses with a neutral density ≥ 28.40 kg m−3, which was considered the WSBW's upper limit throughout the simulation period. The expected WDW warming was only reproduced by the SODA product, whereas the ECCO2 product was able to represent the trends in the WSDW's hydrographic properties. All the assessed ocean reanalyses were able to represent the decrease in the WSBW's density, except the SODA product in the inner Weddell Sea. Improvements in parameterization may have as much impact on the reanalyses assessed as improvements in horizontal resolution primarily because the Southern Ocean lacks in situ data, and the data that are currently available are summer-biased. The choice of the reanalysis product should be made carefully, taking into account the performance, the parameters of interest, and the type of physical processes to be evaluated.

scholarly journals Assessment of the structure and variability of Weddell Sea water masses in distinct ocean reanalysis products

2014 ◽  
Vol 11 (1) ◽  
pp. 497-542 ◽  
Author(s):  
T. S. Dotto ◽  
R. Kerr ◽  
M. M. Mata ◽  
M. Azaneu ◽  
I. Wainer
Keyword(s):  
Deep Water ◽  
Sea Water ◽  
Horizontal Resolution ◽  
Weddell Sea ◽  
Water Masses ◽  
Ocean Reanalysis ◽  
In Situ Data ◽  
Sea Bottom ◽  
Warm Deep Water ◽  
Deep Layers

Abstract. We assessed and evaluated the performance of five ocean reanalysis in reproducing essential hydrographic properties and their associated temporal variability for the Weddell Sea, Antarctica. The products used in this assessment were ECMWF ORAS4, CFSR, MyOcean UR025.4, ECCO2 and SODA. The present study focuses on the Weddell Sea deep layer, which is composed of the following three main water masses: Warm Deep Water (WDW), Weddell Sea Deep Water (WSDW) and Weddell Sea Bottom Water (WSBW). Moreover, all the ocean reanalysis products analyzed showed limited capabilities in representing the surface water masses in the Weddell Sea. The MyOcean UR025.4 product provided the most accurate representation of the structure of the Weddell Sea water masses when compared to observations. The CFSR and ECCO2 products were not able to represent the WSBW throughout the simulation period. The expected WDW warming was only reproduced by the SODA product, while the ECCO2 product was able to represent the WSDW's hydrographic properties trends. All of these ocean reanalysis systems were able to represent the decrease in the WSBW's density. Our results also showed that a simple increase in horizontal resolution does not necessarily imply better representation of the deep layers. Rather, it is needed to observe the physics involved in each model and their parameterizations because the Southern Ocean suffers from the lack of in situ data, and it is biased by summer observations. The choice of the reanalysis product should be made carefully, taking into account the performance, the parameters of interest, and the type of physical processes to be evaluated.

scholarly journals Water masses in the Atlantic Ocean: characteristics and distributions

Ocean Science ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. 463-486
Author(s):  
Mian Liu ◽  
Toste Tanhua
Keyword(s):  
Atlantic Ocean ◽  
Deep Water ◽  
Bottom Water ◽  
Water Mass ◽  
Sea Water ◽  
Weddell Sea ◽  
Water Masses ◽  
Global Ocean ◽  
Intermediate Water ◽  
The North

Abstract. A large number of water masses are presented in the Atlantic Ocean, and knowledge of their distributions and properties is important for understanding and monitoring of a range of oceanographic phenomena. The characteristics and distributions of water masses in biogeochemical space are useful for, in particular, chemical and biological oceanography to understand the origin and mixing history of water samples. Here, we define the characteristics of the major water masses in the Atlantic Ocean as source water types (SWTs) from their formation areas, and map out their distributions. The SWTs are described by six properties taken from the biased-adjusted Global Ocean Data Analysis Project version 2 (GLODAPv2) data product, including both conservative (conservative temperature and absolute salinity) and non-conservative (oxygen, silicate, phosphate and nitrate) properties. The distributions of these water masses are investigated with the use of the optimum multi-parameter (OMP) method and mapped out. The Atlantic Ocean is divided into four vertical layers by distinct neutral densities and four zonal layers to guide the identification and characterization. The water masses in the upper layer originate from wintertime subduction and are defined as central waters. Below the upper layer, the intermediate layer consists of three main water masses: Antarctic Intermediate Water (AAIW), Subarctic Intermediate Water (SAIW) and Mediterranean Water (MW). The North Atlantic Deep Water (NADW, divided into its upper and lower components) is the dominating water mass in the deep and overflow layer. The origin of both the upper and lower NADW is the Labrador Sea Water (LSW), the Iceland–Scotland Overflow Water (ISOW) and the Denmark Strait Overflow Water (DSOW). The Antarctic Bottom Water (AABW) is the only natural water mass in the bottom layer, and this water mass is redefined as Northeast Atlantic Bottom Water (NEABW) in the north of the Equator due to the change of key properties, especially silicate. Similar with NADW, two additional water masses, Circumpolar Deep Water (CDW) and Weddell Sea Bottom Water (WSBW), are defined in the Weddell Sea region in order to understand the origin of AABW.

14C Profiles in the Central Weddell Sea

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 544-556 ◽  
Author(s):  
Peter Schlosser ◽  
Bernd Kromer ◽  
Reinhold Bayer ◽  
K O Münnich
Keyword(s):  
Surface Water ◽  
Potential Temperature ◽  
Radioactive Decay ◽  
Weddell Sea ◽  
Strong Deviation ◽  
Intermediate Layers ◽  
Sea Bottom ◽  
Surface Circulation ◽  
Warm Deep Water ◽  
Deep Layers

14C data from stations in the central Weddell Sea are presented and discussed using additional parameters (potential temperature, salinity and 3He). The low 14C concentrations of the surface water (≈-90‰) are explained by suppressed gas exchange due to ice cover during the winter and rapid turnover of the surface layer caused by entrainment of Warm Deep Water (WDW) with low 14C concentrations. A simple time-dependent balance calculated for the Surface Water (SW) and the underlying Winter Water (WW) can reproduce the 14C concentrations observed in these layers for 1985. The pre-bomb 14C concentrations are estimated at ≈-130‰ for SW and −140‰ for WW. A strong deviation of the SW 14C concentration observed in 1973 from the calculated value suggest a change in surface circulation and/or air/sea exchange during the period before the Weddell Polynya in 1974. The observed 14C concentrations of the Weddell Sea Bottom Water (WSBW; −135 to −150‰) are only slightly higher than those of the WDW showing that the uptake of bomb 14C in the Weddell Sea is limited. The 14C profiles show a minimum at intermediate depths (≈ 1500m) which is caused by radioactive decay and/or penetration of bomb 14C from shallow and deep layers (WDW and WSBW) into intermediate layers.

scholarly journals A rapid transition from ice covered CO<sub>2</sub>–rich waters to a biologically mediated CO<sub>2</sub> sink in the eastern Weddell Gyre

2008 ◽  
Vol 5 (5) ◽  
pp. 1373-1386 ◽  
Author(s):  
D. C. E. Bakker ◽  
M. Hoppema ◽  
M. Schröder ◽  
W. Geibert ◽  
H. J. W. de Baar
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Deep Water ◽  
Dissolved Inorganic Carbon ◽  
Ice Cover ◽  
Weddell Sea ◽  
Sea Surface ◽  
Upward Movement ◽  
Weddell Gyre ◽  
Warm Deep Water

Abstract. Circumpolar Deep Water (CDW), locally called Warm Deep Water (WDW), enters the Weddell Gyre in the southeast, roughly at 25° E to 30° E. In December 2002 and January 2003 we studied the effect of entrainment of WDW on the fugacity of carbon dioxide (fCO2) and dissolved inorganic carbon (DIC) in Weddell Sea surface waters. Ultimately the fCO2 difference across the sea surface drives air-sea fluxes of CO2. Deep CTD sections and surface transects of fCO2 were made along the Prime Meridian, a northwest-southeast section, and along 17° E to 23° E during cruise ANT XX/2 on FS Polarstern. Upward movement and entrainment of WDW into the winter mixed layer had significantly increased DIC and fCO2 below the sea ice along 0° W and 17° E to 23° E, notably in the southern Weddell Gyre. Nonetheless, the ice cover largely prevented outgassing of CO2 to the atmosphere. During and upon melting of the ice, biological activity rapidly reduced surface water fCO2 by up to 100 μatm, thus creating a sink for atmospheric CO2. Despite the tendency of the surfacing WDW to cause CO2 supersaturation, the Weddell Gyre may well be a CO2 sink on an annual basis due to this effective mechanism involving ice cover and ensuing biological fCO2 reduction. Dissolution of calcium carbonate (CaCO3) in melting sea ice may play a minor role in this rapid reduction of surface water fCO2.

scholarly journals On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products

Ocean Science ◽  
2017 ◽  
Vol 13 (6) ◽  
pp. 851-872 ◽  
Author(s):  
Wilton Aguiar ◽  
Mauricio M. Mata ◽  
Rodrigo Kerr
Keyword(s):  
Sea Ice ◽  
Bottom Water ◽  
Deep Convection ◽  
Open Ocean ◽  
Weddell Sea ◽  
Ocean Dynamics ◽  
Antarctic Bottom Water ◽  
Ocean Reanalysis ◽  
Reanalysis Product ◽  
Warm Deep Water

Abstract. Open ocean deep convection is a common source of error in the representation of Antarctic Bottom Water (AABW) formation in ocean general circulation models. Although those events are well described in non-assimilatory ocean simulations, the recent appearance of a massive open ocean polynya in the Estimating the Circulation and Climate of the Ocean Phase II reanalysis product (ECCO2) raises questions on which mechanisms are responsible for those spurious events and whether they are also present in other state-of-the-art assimilatory reanalysis products. To investigate this issue, we evaluate how three recently released high-resolution ocean reanalysis products form AABW in their simulations. We found that two of the products create AABW by open ocean deep convection events in the Weddell Sea that are triggered by the interaction of sea ice with the Warm Deep Water, which shows that the assimilation of sea ice is not enough to avoid the appearance of open ocean polynyas. The third reanalysis, My Ocean University Reading UR025.4, creates AABW using a rather dynamically accurate mechanism. The UR025.4 product depicts both continental shelf convection and the export of Dense Shelf Water to the open ocean. Although the accuracy of the AABW formation in this reanalysis product represents an advancement in the representation of the Southern Ocean dynamics, the differences between the real and simulated processes suggest that substantial improvements in the ocean reanalysis products are still needed to accurately represent AABW formation.

Water masses’ bacterial community structure and microbial activities in the Ross Sea, Antarctica

2010 ◽  
Vol 22 (4) ◽  
pp. 361-370 ◽  
Author(s):  
Mauro Celussi ◽  
Andrea Bergamasco ◽  
Bruno Cataletto ◽  
Serena Fonda Umani ◽  
Paola Del Negro
Keyword(s):  
Community Structure ◽  
Bacterial Community ◽  
Deep Water ◽  
Bacterial Community Structure ◽  
Sea Water ◽  
Ross Sea ◽  
Water Masses ◽  
Shelf Water ◽  
Microbial Activities ◽  
Ice Shelf

AbstractDuring the summer 2005/06, an oceanographic cruise was carried out in the Ross Sea, from Cape Adare, through the Terra Nova Bay polynya to the eastern edge of the Ross Ice Shelf. We analysed microbial activities (prokaryotic carbon production, protease, phosphatase, beta-glucosidase and lipase activity) and bacterial community structure (using Denaturing Gradient Gel Electrophoresis - DGGE) in order to establish if differences in bacterioplankton assemblages and their metabolic requirements occur within the five Ross Sea water masses: Antarctic Surface Waters (AASW), High Salinity Shelf Water (HSSW), Ice Shelf Water (ISW), Antarctic Bottom Water (AABW), Circumpolar Deep Water (CDW). Differences in activities were found between the highly active AASW and all the other water bodies. A Principal Component Analysis highlighted two main gradients: in the Cape Adare area (AASWn, CDW and AABW) higher phosphatase, lipase and glycolytic activities, increasing towards the surface, were identified, whereas in the southern sector of the basin [AASWs and (m)HSSW] higher leucine uptake and polypeptide degradation characterized the second gradient. DGGE fingerprinting showed for the first time that different water masses harboured diverse bacterial communities, highlighting the high specificity of deep water assemblages.Alpha- andGammaproteobacteriarepresented the main phylogenetic groupings in all samples and no substantial difference in the phylogenetic composition of assemblages was found between different water masses.

scholarly journals Modification by lateral mixing of the Warm Deep Water entering the Weddell Sea in the Maud Rise region

2010 ◽  
Vol 61 (1) ◽  
pp. 51-68 ◽  
Author(s):  
Harry Leach ◽  
Volker Strass ◽  
Boris Cisewski
Keyword(s):  
Deep Water ◽  
Weddell Sea ◽  
Warm Deep Water ◽  
Lateral Mixing ◽  
Maud Rise

scholarly journals Dissolved Fe across the Weddell Sea and Drake Passage: impact of DFe on nutrients uptake in the Weddell Sea

2013 ◽  
Vol 10 (4) ◽  
pp. 7433-7489 ◽  
Author(s):  
M. B. Klunder ◽  
P. Laan ◽  
H. J. W. De Baar ◽  
I. Neven ◽  
R. Middag ◽  
...  
Keyword(s):  
Deep Water ◽  
Bottom Water ◽  
Drake Passage ◽  
Weddell Sea ◽  
Dust Deposition ◽  
Scotia Sea ◽  
Ice Melt ◽  
Sea Bottom ◽  
Poc Export ◽  
Bottom Waters

Abstract. This manuscript reports the first full depth distributions of dissolved iron (DFe) over a high resolution Weddell Sea and Drake Passage transect. Very low dissolved DFe concentrations (0.01–0.1 nM range) were observed in the surface waters in the Weddell Sea, and within the Polar regime in the Drake Passage. Locally, enrichment in surface DFe was observed, likely due to recent ice melt (Weddell Sea) or dust deposition (Drake Passage). In the Weddell Sea, the low DFe concentrations can be partly explained by high POC export and/or primary production (indicated by chlorophyll fluorescence). As expected, in high DFe regions a strong silicate drawdown compared to nitrate drawdown was observed. However, this difference in drawdown between these nutrients appears not related to biological activity on the Peninsula shelf. In the Western Weddell Sea transect, with relatively small diatoms, no relationship between N:P and N:Si removal ratios and DFe was observed. For comparison, nutrient depletion is also presented for a transect along the Greenwich Meridian (Klunder et al., 2011), where diatoms are significantly larger, the N:P and N:Si removal ratio increased with increasing DFe. These findings confirm the important role of DFe in Southern Ocean (biologically mediated) nutrient cycles. Over the shelf around the Antarctic Peninsula, higher DFe concentrations (> 1.5 nM) were observed. These elevated concentrations of Fe were transported into Drake Passage along isopycnal surfaces. At the South American continent, high (> 2 nM) DFe concentrations were caused by fluvial/glacial input of DFe. On the Weddell Sea side of the Peninsula region, formation of deep water (by downslope convection) caused relatively high Fe (0.6–0.8 nM) concentrations in the bottom waters relative to the water masses at mid depth (0.2–0.4 nM). During transit of Weddell Sea Bottom Water to Drake Passage, through the Scotia Sea, extra DFe is taken up from seafloor sources, resulting in highest bottom water concentrations in the southernmost part of the Drake Passage of > 1 nM. The Weddell Sea Deep Water concentrations (~ 0.32 nM) were consistent with the lowest DFe concentrations observed in Atlantic AABW.

Representation of the Weddell Sea deep water masses in the ocean component of the NCAR-CCSM model

2009 ◽  
Vol 21 (3) ◽  
pp. 301-312 ◽  
Author(s):  
Rodrigo Kerr ◽  
Ilana Wainer ◽  
Mauricio M. Mata
Keyword(s):  
Deep Water ◽  
Climate Models ◽  
Weddell Sea ◽  
Water Masses ◽  
Water Type ◽  
Climate System Model ◽  
Mass Distributions ◽  
Meridian Section ◽  
Greenwich Meridian ◽  
Multiparameter Analysis

AbstractWe examine Weddell Sea deep water mass distributions with respect to the results from three different model runs using the oceanic component of the National Center for Atmospheric Research Community Climate System Model (NCAR-CCSM). One run is inter-annually forced by corrected NCAR/NCEP fluxes, while the other two are forced with the annual cycle obtained from the same climatology. One of the latter runs includes an interactive sea-ice model. Optimum Multiparameter analysis is applied to separate the deep water masses in the Greenwich Meridian section (into the Weddell Sea only) to measure the degree of realism obtained in the simulations. First, we describe the distribution of the simulated deep water masses using observed water type indices. Since the observed indices do not provide an acceptable representation of the Weddell Sea deep water masses as expected, they are specifically adjusted for each simulation. Differences among the water masses’ representations in the three simulations are quantified through their root-mean-square differences. Results point out the need for better representation (and inclusion) of ice-related processes in order to improve the oceanic characteristics and variability of dense Southern Ocean water masses in the outputs of the NCAR-CCSM model, and probably in other ocean and climate models.

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