Pubblicato in: Problemia Energetici, Scienza & Tecnica

Calotta Artica. Spessore del ghiaccio in aumento. Qualcuno lo dica a Greta.

Giuseppe Sandro Mela.


2021-11-08__ Polar Portal 010

La campagna mediatica sul ‘clima’ propone con toni sempre più melodrammatici lo apocalittico surriscaldamento del globo terraqueo. L’Oceano Artico disciolto, con innalzamento dei ivelli del mare. Una catastrofe immane.

Al contrario, lo spessore dei ghiacci artici, anziché diminuire, è in costante aumento fatto che questo che non corrobora simili asserzioni.

2021-11-08__ Polar Portal 011

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                         The state of the sea ice is determined by its extent, thickness and volume

 The ice cover in the Arctic grows throughout the winter, before peaking in March. Melting picks up pace during the spring as the sun gets stronger, and in September the extent of the ice cover is typically only around one third of its winter maximum.

Differences may occur in terms of the position of the edge of the ice in the two maps, “Extent of the sea ice” and “Thickness and volume of the sea ice”, as the model calculations do not always correspond exactly to the satellite sensors’ registration of the extent of the ice.

Ice concentrations are based on satellite data and are from the Ocean and Sea Ice Satellite Application Facility project (OSISAF).

The thickness of the ice shown is calculated by means of the HYCOM-CICE model of sea ice at DMI. The model calculates various oceanographic values, including sea ice, in a grid with cells of 10 x 10 square km. The model is driven by meteorological data from ECMWF (European Centre for Medium-Range Weather Forecasts). In each grid cell the ice is classified into 5 thickness categories, with thickness, concentration, movement and heat balance of the ice being calculated for each category. The map of the ice thickness shows the mean thickness of ice in each grid cell.

The graph on the right shows the annual variation of the volume of the sea ice in the Northern Hemisphere, excluding the Baltic Sea and the Pacific. The volume of the ice is calculated on the basis of the ice thicknesses from the HYCOM-CICE model. In each grid cell the volume is calculated as thickness multiplied with concentration and with area, with contributions from all grid cells to the total volume. The grey band around the climatologic mean value corresponds to plus/minus one standard deviation based on the 10-year average 2004-2013.