scholarly journals Interannual Variability of Sea Surface Height over the Black Sea: Relation to Climatic Patterns

2008 ◽  
Vol 12 (10) ◽  
pp. 1-11 ◽  
Author(s):  
A. Birol Kara ◽  
Charlie N. Barron ◽  
Alan J. Wallcraft ◽  
Temel Oguz
Keyword(s):  
Black Sea ◽  
Large Scale ◽  
Mesoscale Eddy ◽  
Strong Relationship ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Optimal Interpolation ◽  
Altimeter Data ◽  
The Black Sea ◽  
Teleconnection Patterns

Abstract Sea surface height (SSH) variability is presented over the Black Sea during 1993–2005. The 1/4° × 1/4° resolution daily SSH fields are formed using optimal interpolation of available altimeter data. SSH variability reveals distinct maxima in the eastern and western basins, reflecting variations in the corresponding gyres. A joint examination of SSH and sea surface temperature (SST) indicates strong relationship between the two only in winter, with correlations as high as 0.6 or more. This would reflect a steric change in sea surface height due to thermal expansion averaged over a relatively deep winter mixed layer. Newly developed SSH fields also demonstrate a switch to the positive mode of SSH starting from the end of 1996 lasting ≈4 yr. Such a climatic shift is found to be strongly related to large-scale teleconnection patterns. Finally, the daily SSH and SST anomaly fields presented in this paper can supplement various applications in the Black Sea, such as examination of biological production and mesoscale eddy dynamics.

Contributions of Wind Forcing and Surface Heating to Interannual Sea Level Variations in the Atlantic Ocean

2006 ◽  
Vol 36 (9) ◽  
pp. 1739-1750 ◽  
Author(s):  
Cécile Cabanes ◽  
Thierry Huck ◽  
Alain Colin de Verdière
Keyword(s):  
Atlantic Ocean ◽  
Sea Level ◽  
Wind Stress ◽  
Large Scale ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Altimeter Data ◽  
Local Response ◽  
Sea Level Variability ◽  
Sea Level Variations

Abstract Interannual sea surface height variations in the Atlantic Ocean are examined from 10 years of high-precision altimeter data in light of simple mechanisms that describe the ocean response to atmospheric forcing: 1) local steric changes due to surface buoyancy forcing and a local response to wind stress via Ekman pumping and 2) baroclinic and barotropic oceanic adjustment via propagating Rossby waves and quasi-steady Sverdrup balance, respectively. The relevance of these simple mechanisms in explaining interannual sea level variability in the whole Atlantic Ocean is investigated. It is shown that, in various regions, a large part of the interannual sea level variability is related to local response to heat flux changes (more than 50% in the eastern North Atlantic). Except in a few places, a local response to wind stress forcing is less successful in explaining sea surface height observations. In this case, it is necessary to consider large-scale oceanic adjustments: the first baroclinic mode forced by wind stress explains about 70% of interannual sea level variations in the latitude band 18°–20°N. A quasi-steady barotropic Sverdrup response is observed between 40° and 50°N.

The new Black Sea Reanalysis System within CMEMS

2021 ◽  
Author(s):  
Leonardo Lima ◽  
Stefania Angela Ciliberti ◽  
Ali Aydogdu ◽  
Romain Escudier ◽  
Simona Masina ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Sea Level ◽  
Black Sea ◽  
General Circulation ◽  
Circulation Model ◽  
Sea Surface Height ◽  
Sea Surface ◽  
The Black Sea ◽  
Freshwater Flux ◽  
Sea Level Anomaly

<p>Ocean reanalyses are becoming increasingly important to reconstruct and provide an overview of the ocean state from the past to the present-day. These products require advanced scientific methods and techniques to produce a more accurate ocean representation. In the scope of the Copernicus Marine Environment Monitoring Service (CMEMS), a new Black Sea (BS) reanalysis, BS-REA (BSE3R1 system), has been produced by using an advanced variational data assimilation method to combine the best available observations with a state-of-the-art ocean general circulation model. The hydrodynamical model is based on Nucleus for European Modeling of the Ocean (NEMO, v3.6), implemented for the BS domain with horizontal resolution of 1/27° x 1/36°, and 31 unevenly distributed vertical levels. NEMO is forced by atmospheric surface fluxes computed via bulk formulation and forced by ECMWF ERA5 atmospheric reanalysis product. At the surface, the model temperature is relaxed to daily objective analysis fields of sea surface temperature from CMEMS SST TAC. The exchange with Mediterranean Sea is simulated through relaxation of the temperature and salinity near Bosporus toward a monthly climatology computed from a high-resolution multi-year simulation, and the barotropic Bosporus Strait transport is corrected to balance the variations of the freshwater flux and the sea surface height measured by multi-satellite altimetry observations. A 3D-Var ocean data assimilation scheme (OceanVar) is used to assimilate sea level anomaly along-track observations from CMEMS SL TAC and available in situ vertical profiles of temperature and salinity from both SeaDataNet and CMEMS INS TAC products. Comparisons against the previous Black Sea reanalysis (BSE2R2 system) show important improvements for temperature and salinity, such that errors have significantly decreased (about 50%). Temperature fields present a continuous warming in the layer between 25-150 m, within which there is the presence of the Black Sea Cold Intermediate Layer (CIL). SST exhibits a positive bias and relatively higher root mean square error (RMSE) values are present in the summer season. Spatial maps of sea level anomaly reveal the largest RMSE close to the shelf areas, which are related to the mesoscale activity along the Rim current. The BS-REA catalogue includes daily and monthly means for 3D temperature, salinity, and currents and 2D sea surface height, bottom temperature, mixed layer fields, from Jan 1993 to Dec 2019.  The BSE3R1 system has produced very accurate estimates which makes it very suitable for assessing more realistic climate trends and indicators for important ocean properties.</p>

scholarly journals How Does Solar Attenuation Depth Affect the Ocean Mixed Layer? Water Turbidity and Atmospheric Forcing Impacts on the Simulation of Seasonal Mixed Layer Variability in the Turbid Black Sea*

2005 ◽  
Vol 18 (3) ◽  
pp. 389-409 ◽  
Author(s):  
A. Birol Kara ◽  
Alan J. Wallcraft ◽  
Harley E. Hurlburt
Keyword(s):  
Solar Radiation ◽  
Black Sea ◽  
Mixed Layer ◽  
Sea Surface ◽  
Shortwave Radiation ◽  
Altimeter Data ◽  
The Black Sea ◽  
Upper Ocean ◽  
Clear Water ◽  
Water Turbidity

Abstract A fine-resolution (≈3.2 km) Hybrid Coordinate Ocean Model (HYCOM) is used to investigate the impact of solar radiation attenuation with depth on the predictions of monthly mean sea surface height (SSH), mixed layer depth (MLD), buoyancy and heat fluxes, and near-sea surface circulation as well. The model uses spatially and temporally varying attenuation of photosynthetically available radiation (kPAR) climatologies as processed from the remotely sensed Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) to take water turbidity into account in the Black Sea. An examination of the kPAR climatology reveals a strong seasonal cycle in the water turbidity, with a basin-averaged annual climatological mean value of 0.19 m−1 over the Black Sea. Climatologically forced HYCOM simulations demonstrate that shortwave radiation below the mixed layer can be quite different based on the water turbidity, thereby affecting prediction of upper-ocean quantities in the Black Sea. The clear water constant solar attenuation depth assumption results in relatively deeper MLD (e.g., ≈+15 m in winter) in comparison to standard simulations due to the unrealistically large amount of shortwave radiation below the mixed layer, up to 100 W m−2 during April to October. Such unrealistic sub–mixed layer heating causes weaker stratification at the base of the mixed layer. The buoyancy gain associated with high solar heating in summer effectively stabilizes the upper ocean producing shallow mixed layers and elevated SSH over the most of the Black Sea. In particular, the increased stability resulting from the water turbidity reduces vertical mixing in the upper ocean and causes changes in surface-layer currents, especially in the easternmost part of the Black Sea. Monthly mean SSH anomalies from the climatologically forced HYCOM simulations were evaluated against a monthly mean SSH anomaly climatology, which was constructed using satellite altimeter data from TOPEX/ Poseidon (T/P), Geosat Follow-On (GFO), and the Earth Remote Sensing Satellite-2 (ERS-2) over 1993–2002. Model–data comparisons show that the basin-averaged root-mean-square (rms) difference is ≈4 cm between the satellite-based SSH climatology and that obtained from HYCOM simulations using spatial and temporal kPAR fields. In contrast, when all solar radiation is absorbed at the sea surface or clear water constant solar attenuation depth values of 16.7 m are used in the model simulations, the basin-averaged SSH rms difference with respect to the climatology is ≈6 cm (≈50% more). This demonstrates positive impact from using monthly varying solar attenuation depths in simulating upper-ocean quantities in the Black Sea. The monthly mean kPAR and SSH anomaly climatologies presented in this paper can also be used for other Black Sea studies.

Evolution of the Black Sea Physical Analysis and Forecasting System within CMEMS

2021 ◽  
Author(s):  
Stefania Angela Ciliberti ◽  
Eric Jansen ◽  
Diana Azevedo ◽  
Murat Gunduz ◽  
Mehmet Ilicak ◽  
...  
Keyword(s):  
Black Sea ◽  
Mixed Layer Depth ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Danube River ◽  
Core Model ◽  
The Black Sea ◽  
Physical Analysis ◽  
Marmara Sea ◽  
Forecasting System

<p>The Black Sea physical analysis and Forecasting System (BSFS) is part of the Black Sea Monitoring and Forecasting Centre (BS-MFC) for the Copernicus Marine Service (CMEMS). It provides analysis every day analysis and 10 days forecast fields for the blue ocean variables (including temperature, salinity, sea surface height, mixed layer depth and currents) in the Black Sea region since. In this work, we present the new version of the operational system that will be part of the next CMEMS  release. The hydrodynamical core model is based on NEMO v4.0, solved on 1/40º horizontal resolution spatial grid (including the overall Black Sea, the Bosporus Strait and part of the Marmara Sea) and 121 vertical levels with z-star. The core model uses ECMWF analysis and forecast atmospheric forcing and GPCP monthly climatological precipitation for computing heat, water and momentum fluxes. A total number of 72 rivers is accounted, as monthly climatology provided by SESAME project. The model implements a new representation of the Danube River with interannual river discharge datasets provided by the National Institute of Hydrology and Water Management. One of the main innovations of this system is the opening of the Bosporus Strait by using a box-approach in a portion of the Marmara Sea: it is achieved thanks to high resolution temperature, salinity, sea surface height, zonal and meridional velocity solutions provided by a novel implementation of the Marmara Sea model including straits based on Shyfem: it represents the optimal interface between the Mediterranean and the Black Sea. The hydrodynamical model is online coupled to an upgraded version of the OceanVar, the CMCC data assimilation scheme, able to assimilate SLA L3 satellite data, T/S in-situ profiles and SST from CMEMS TACs. The contribution focuses on model setup description, processing system and validation. To evaluate BSFS pre-operational run and monitor the operational production, we provide metrics as proposed within GODAE/Oceanpredict and MERSEA/MyOcean (which includes CLASS 1, 2 and 4 metrics).</p>

scholarly journals Meridional displacement of the Antarctic Circumpolar Current

2014 ◽  
Vol 372 (2019) ◽  
pp. 20130273 ◽  
Author(s):  
Sarah T. Gille
Keyword(s):  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Altimeter Data ◽  
Eddy Heat Transport ◽  
Circumpolar Current

Observed long-term warming trends in the Southern Ocean have been interpreted as a sign of increased poleward eddy heat transport or of a poleward displacement of the entire Antarctic Circumpolar Current (ACC) frontal system. The two-decade-long record from satellite altimetry is an important source of information for evaluating the mechanisms governing these trends. While several recent studies have used sea surface height contours to index ACC frontal displacements, here altimeter data are instead used to track the latitude of mean ACC transport. Altimetric height contours indicate a poleward trend, regardless of whether they are associated with ACC fronts. The zonally averaged transport latitude index shows no long-term trend, implying that ACC meridional shifts determined from sea surface height might be associated with large-scale changes in sea surface height more than with localized shifts in frontal positions. The transport latitude index is weakly sensitive to the Southern Annular Mode, but is uncorrelated with El Niño/Southern Oscillation.

Role of suspended matter in controlling beryllium-7 (7Be) in the Black Sea surface layer

2021 ◽  
pp. 103513
Author(s):  
Dmitrii A. Kremenchutskii ◽  
Gennady F. Batrakov ◽  
Illarion I. Dovhyi ◽  
Yury A. Sapozhnikov
Keyword(s):  
Surface Layer ◽  
Black Sea ◽  
Suspended Matter ◽  
Sea Surface ◽  
The Black Sea

The global structure of the annual and semiannual sea surface height variability from Geosat altimeter data

1992 ◽  
Vol 97 (C11) ◽  
pp. 17813-17828 ◽  
Author(s):  
Gregg A. Jacobs ◽  
George H. Born ◽  
Mike E. Parke ◽  
Patrick C. Allen
Keyword(s):  
Sea Surface Height ◽  
Global Structure ◽  
Sea Surface ◽  
Altimeter Data

scholarly journals On the Relationship between Regional Ocean Heat Content and Sea Surface Height

2017 ◽  
Vol 30 (22) ◽  
pp. 9195-9211 ◽  
Author(s):  
John T. Fasullo ◽  
Peter R. Gent
Keyword(s):  
Time Scales ◽  
Low Frequency ◽  
Heat Content ◽  
Sea Surface Height ◽  
Ocean Heat Content ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Altimeter Data ◽  
Model Control ◽  
The Relationship

Abstract An accurate diagnosis of ocean heat content (OHC) is essential for interpreting climate variability and change, as evidenced for example by the broad range of hypotheses that exists for explaining the recent hiatus in global mean surface warming. Potential insights are explored here by examining relationships between OHC and sea surface height (SSH) in observations and two recently available large ensembles of climate model simulations from the mid-twentieth century to 2100. It is found that in decadal-length observations and a model control simulation with constant forcing, strong ties between OHC and SSH exist, with little temporal or spatial complexity. Agreement is particularly strong on monthly to interannual time scales. In contrast, in forced transient warming simulations, important dependencies in the relationship exist as a function of region and time scale. Near Antarctica, low-frequency SSH variability is driven mainly by changes in the circumpolar current associated with intensified surface winds, leading to correlations between OHC and SSH that are weak and sometimes negative. In subtropical regions, and near other coastal boundaries, negative correlations are also evident on long time scales and are associated with the accumulated effects of changes in the water cycle and ocean dynamics that underlie complexity in the OHC relationship to SSH. Low-frequency variability in observations is found to exhibit similar negative correlations. Combined with altimeter data, these results provide evidence that SSH increases in the Indian and western Pacific Oceans during the hiatus are suggestive of substantial OHC increases. Methods for developing the applicability of altimetry as a constraint on OHC more generally are also discussed.

Influence of Currents and Atmospheric Circulation on the Efficiency of European Anchovy Fishing during its Wintering off the Black Sea Coast of the Krasnodar Territory

2021 ◽  
Author(s):  
B. N. Panov ◽  
E. O. Spiridonova ◽  
◽  
Keyword(s):  
Black Sea ◽  
Atmospheric Transport ◽  
Mesoscale Eddy ◽  
The Black Sea ◽  
Short Term ◽  
European Anchovy ◽  
The North ◽  
Daily Data ◽  
Black Sea Coast ◽  
Sea Coast

Russian fishermen harvest European anchovy primarily off the Black Sea coast of the Krasnodar Territory during its wintering and wintering migrations. At wintering grounds, temperature conditions become a secondary factor in determining the behaviour of commercial concentration of European anchovy, with wind and currents being the primary factors. Therefore, the aim of this work is to determine the potential use of daily data on water circulation and local atmospheric transport in short-term (1–7 days) forecasting of European anchovy fishing in the Black Sea. The research used the European anchovy fishery monitoring materials for January – March 2019, as well as daily maps of the Black and Azov Seas level anomalies (from satellite altimetry data) and surface atmospheric pressure and temperature in Europe (analysis) for the mentioned period. The dynamics of the catch rate and its relation to altimetry and atmospheric transport indicators in the north-eastern part of the Black Sea were investigated using graphical and correlation methods. This analysis showed that the main factor contributing to increased catches is intensification of northwest currents in the coastal 60-km zone. The effect of atmospheric transport on fishing efficiency depends on the mesoscale eddy structure of the nearshore current field. In the presence of an intense northwest current in the fishing area, southwest atmospheric transports have a positive effect on fishing, while in the presence of an anticyclonic meander of currents, northeast atmospheric transports become effective. The presence of maximum significant relationships when the determinants of fishing performance are shifted by 1–7 days allows making short-term predictions of fishing efficiency.

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