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Ocean Surface Topography from Space
The Mediterranean and Black Seas: Analysis of Large Sea Level Anomalies


Denis Volkov - (University of Miami, RSMAS)

Co-Investigator(s)/Science Principal Investigator(s):
  Felix Landerer
(California Institute of Technology - JPL)


Satellite altimetry observations by OSTM/Jason-2 and Envisat missions have revealed extremely large sea level fluctuations that occurred in the Mediterranean and Black seas in the winters of 2010 and 2011. During this time the basin-wide non-seasonal sea level in the Mediterranean Sea increased by about 10 cm reaching the record maximum during the observational period. Similar anomalies were observed in bottom pressure derived from the gravity field measurements by the NASA's GRACE twin satellites. In the Black Sea, the associated sea level anomalies exceeded 20 cm lagging behind the sea level anomalies in the Mediterranean Sea by about 1 month. Understanding and quantifying the dynamics of sea level variations in these semi-enclosed seas is important because of the possible amplified sea level response to climate forcings, and because of the densly populated coasts in the region. Sea level is a natural integral indicator of climate variability and its present-day rate of rise is one of the most damaging and costly consequences of global change.

With the proposed research, we intend to achieve the following objectives:

  1. to understand what caused the unprecedented sea level rise in the Mediterranean and Black seas in 2010 and 2011,
  2. to determine the relative contribution of steric and mass effects to the sea level variability in the region on a broad spectrum of time-scales,
  3. to quantify the influence of atmospheric circulation in the subtropical North Atlantic on sea level in the Mediterranean Sea,
  4. to investigate the role of the total freshwater balance in forcing the changes of sea level, and
  5. to establish the statistical and dynamical relationship between the sea level fluctuations in the Mediterranean and Black seas.

The proposed research will focus on time scales from months to interannual variability, and use observational data as well as models: delayed and real-time along-track and gridded satellite altimetry data, GRACE measurements, tide gauge records, in situ hydrography, river runoff, atmospheric reanalysis and ocean data synthesis products, and numerical simulations.

To achieve the aforementioned objectives, the following tasks will be accomplished:

  1. regional altimetric and GRACE measurements will be optimized,
  2. the monthly river discharge into the Mediterranean and Black seas will be quantified,
  3. the components of sea level budget will be estimated,
  4. the steric and mass effects will be deduced by combining altimetry, ocean gravity, and available in situ measurements,
  5. the relationship between the atmospheric circulation over the subtropical North Atlantic and the Mediterranean sea level, and sea level in the Mediterranean and Black seas will be established and quantified by using numerical sensitivity experiments.

We expect that the proposed research will provide robust observational and model-based estimates for the factors responsible for the sea level variability in the Mediterranean and Black seas, including the observed extreme sea level events in 2010 and 2011. By establishing relationships between the changes of sea level in the Mediterranean and Black seas, and the large-scale climate forcing, the results based on contemporary observations can be used to assess the sensitivity of sea level variations in this region under future climate conditions. The proposed research directly addresses the objectives of five (out of eight) research themes of the OSTST by

  1. supporting studies in physical oceanography utilizing the combined TP/Jason-1/Jason-2 data jointly with other satellite, in situ, and model data,
  2. supporting studies of higher-resolution merged altimetry data sets,
  3. investigating the use of gravity mission data with altimetry for improving the understanding of the ocean barotropic variability,
  4. exploring operational applications of satellite altimetry with a requirement for near real-time data, and
  5. complimenting the large river mouth surveys.

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