50 research outputs found
The effect of the NAO on sea level and on mass changes in the Mediterranean Sea
No full text[1] Sea level in the Mediterranean Sea over the period 1993-2011 is studied on the basis of altimetry, temperature, and salinity data and gravity measurements from Gravity Recovery and Climate Experiment (GRACE) (2002-2010). An observed increase in sea level corresponds to a linear sea level trend of 3.0 ± 0.5 mm/yr dominated by the increase in the oceanic mass in the basin. The increase in sea level does not, however, take place linearly but over two 2-3 year periods, each contributing 2-3 cm of sea level. Variability in the basin sea level and its mass component is dominated by the winter North Atlantic Oscillation (NAO). The NAO influence on sea level is primarily linked with atmospheric pressure changes and local wind field changes. However, neither the inverse barometer correction nor a barotropic sea level model forced by atmospheric pressure and wind can remove fully the NAO influence on the basin sea level. Thus, a third contributing mechanism linked with the NAO is suggested. During winter 2010, a low NAO index caused a basin sea level increase of 12 cm which was almost wholly due to mass changes and is evidenced by GRACE. About 8 cm of the observed sea level change can be accounted for as due to atmospheric pressure and wind changes. The residual 4 cm of sea level change is caused by the newly identified contribution. The physical mechanisms that may be responsible for this additional contribution are discussed. © 2013 American Geophysical Union. All Rights Reserved
Hydrographic vs. Dynamic Description of a Basin: The Example of Baroclinic Motion in the Ionian Sea
No full textThe Ionian Sea is a crucial intersection for various water masses in the Mediterranean. Its hydrography and dynamics play a significant role in the seawater budgets and biogeochemistry of the neighboring sub-basins. Multiple theories have been formulated to gain a better understanding of the Ionian dynamics. These theories primarily attribute the variability of the near-surface Ionian circulation to internal processes. Here, we utilize horizontal currents and temperature–salinity profiles from the Copernicus reanalysis to examine the contribution of baroclinic modes to the variability of the basin horizontal circulation. Our findings demonstrate that, although the basin vertical structure is characterized by three layers, the primary patterns of the Ionian circulation can be attributed to the first baroclinic mode. This mode, along with the barotropic mode, accounts for over 85% of the overall variability in the Ionian circulation, suggesting that only one of the three interfaces separating the different water masses in the basin is dynamically active. We estimate the depth of this interface to be about 490 m. Additionally, our analysis shows that more than 90% of the kinetic energy over the water column is localized above this interface, indicating that the deep layer of the Ionian is dynamically nearly inert
Decadal variability of net water flux at the Mediterranean Sea Gibraltar Strait
No full textLong-term variability of the net water flux into the Mediterranean Sea at the Gibraltar Strait over the period 1960-2009 is explored based on an approach combining multiple observational datasets and results from a regional climate model simulation. The approach includes deriving Gibraltar net inflow from the application of the Mediterranean Sea water budget equation using observationally based estimates of mass variation, evaporation, precipitation and simulated river discharge and Bosphorus Strait water fluxes. This derivation is compared with results from a simulation using the PROTHEUS regional ocean-atmosphere coupled model considering both individual water cycle terms and overall Gibraltar water flux.Results from both methodologies point to an increase in net water flux at Gibraltar over the period 1970-2009 (0.8 +/- 0.2. mm/mo per year based on the observational approach). Simulated Gibraltar net water flux shows decadal variability during 1960-2009 including a net Gibraltar water flux decrease during 1960-1970 before the 1970-2009 increase.Decadal variations in net evaporation at the sea-surface, such as the increase during 1970-2009, appear to drive the changes in net inflow at Gibraltar, while river runoff and net inflow at the Bosphorus Strait have a modulating effect. Mediterranean Sea mass changes are seen to be relatively small compared to water mass fluxes at the sea surface and do not show a long-term trend over 1970-2009. The Atlantic Multi-decadal Oscillation (AMO) and the North Atlantic Oscillation (NAO) are relevant indirect influences on net water flux at Gibraltar via the influence they bear on regional evaporation, precipitation and runoff. © 2012 Elsevier B.V.
The ENEA-REG system (v1.0), a multi-component regional Earth system model: sensitivity to different atmospheric components over the Med-CORDEX (Coordinated Regional Climate Downscaling Experiment) region
No full textIn this study, a new regional Earth system model is developed and applied to
the Med-CORDEX (Coordinated Regional Climate Downscaling Experiment) region. The ENEA-REG system is made up of two interchangeable
regional climate models as atmospheric components (RegCM, REGional Climate Model, and WRF, Weather Research and Forecasting), a river
model (Hydrological Discharge, HD), and an ocean model (Massachusetts Institute of
Technology General Circulation Model, MITgcm); processes taking place at the land
surface are represented within the atmospheric models with the possibility
to use several land surface schemes of different complexity. The coupling
between these components is performed through the RegESM driver.
Here, we present and describe our regional Earth system model and evaluate
its components using a multidecadal hindcast simulation over the period
1980–2013 driven by ERA-Interim reanalysis. We show that the atmospheric
components correctly reproduce both large-scale and local features of the
Euro-Mediterranean climate, although we found some remarkable biases: in
particular, WRF has a significant cold bias during winter over the
northeastern bound of the domain and a warm bias in the whole continental
Europe during summer, while RegCM overestimates the wind speed over the
Mediterranean Sea.
Similarly, the ocean component correctly reproduces the analyzed ocean
properties with performances comparable to the state-of-art coupled regional
models contributing to the Med-CORDEX initiative.
Our regional Earth system model allows studying the Euro-Mediterranean
climate system and can be applied to both hindcast and scenario simulations.</p
Strategic Research Agenda towards innovation in Blue Energy
No full textThis document contains the Strategic Research Agenda to Innovation on Blue Energy developed in the framework of the PELAGOS project (D.4.2.1). Relying on both the current Research & Innvation guidelines and priorities established at European level for exploitating in the most effective way the potential of Ocean Energy and the knowledge acquired the activities of PELAGOS project at Mediterranean level, this document considers the strategic focus areas related to the most promising Marine Renewables Energy technologies in the Mediterranean area
Modelling present and future climate in the Mediterranean Sea: a focus on sea-level change
No full textWe present results of three simulations of the Mediterranean Sea climate: a hindcast, a historical run, and a RCP8.5 scenario simulation reaching the year 2100. The simulations are performed with MED16, a new, tide-including implementation of the MITgcm model, which covers the Mediterranean—Black Sea system with a resolution of 1/16°, further increased at the Gibraltar and Turkish Straits. Validation of the hindcast simulation against observations and numerical reanalyses has given excellent results, proving that the model is also capable of reproducing near-shore sea level variations. Moreover, the spatial structure of the elevation field compares well with altimetric observations, especially in the Western basin, due to the use of improved sea level information at the Atlantic lateral boundary and to the adequate treatment of the complex, hydraulically driven dynamics across the Gibraltar Strait. Under the RCP8.5 future scenario, the temperature is projected to generally increase while the surface salinity decreases in the portion of the Mediterranean affected by the penetration of the Atlantic stream, and increases elsewhere. The warming of sea waters results in the partial inhibition of deep-water formation. The scenario simulation allows for a detailed characterization of the regional patterns of future sea level, arising from ocean dynamics, and indicates a relative sinking of the Mediterranean with respect to the Atlantic more pronounced than the current one
