HYMEX SOP2

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Background and objectives

The second intensive measurement campaign (SOP2 – Special observation period 2) of the HyMeX programme was devoted to the observation and modelling of the formation of dense water and oceanic convection in the Gulf of Lion, associated with intense air-sea flows under the Mistral and Tramontane regimes. Indeed, these dry regional winds, cold in winter from the land to the sea, produce important air-sea exchanges, in particular a strong evaporation and a cooling which increases the density of the surface oceanic waters. A progressive destabilisation of the water column under the effect of repeated and prolonged gales can lead at the end of winter to the triggering of oceanic convection affecting the whole water column in regions subject to these regional wind regimes, such as the Gulf of Lion.

These areas of oceanic convection and dense water formation are the drivers of the entire thermohaline circulation in the Mediterranean. The vertical mixing of the entire water column also brings oxygen to the deeper layers, while nutrients, which are abundant at depth, are brought up to the surface layers. This phenomenon, whose occurrence and amplitude vary greatly from one year to the next, has a major impact on the dynamics of marine ecosystems, the marine food chain and fishing resources.

Location and dates

The campaign took place from 27 January to 15 March 2013 in the Gulf of Lion, a major area of dense water formation in the Mediterranean. The Mistral and Tramontana winds were strong, with eight episodes of strong winds during the month and a half of the campaign. These conditions were conducive to the formation of dense water and oceanic convection affecting the entire water column in the Gulf of Lion.

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Thematiques :climate
Typologie de projet :Campaigns

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