Water temperatures have become very cool in the Mediterranean between Languedoc-Roussillon and Provence, sometimes dipping below 20°C. The wind is to blame, causing upwelling. What is upwelling?
Over the past few days, holidaymakers in south-eastern France may have been surprised by the water temperature in the Mediterranean: it’s certainly very pleasant between the Côte d’Azur and Corsica, often reaching over 25°C; but around the Gulf of Lion, between Languedoc-Roussillon and Provence, as far as the Toulon roadstead, it barely reaches 20 to 22°C at most.
On the Sète side, the water was only 18°C (64°F) on Tuesday, just like yesterday near Béziers. A stark contrast compared to the air temperature, which can sometimes exceed 35°C (95°F) on the sand, in the shade of a parasol, as in the Perpignan region. The risk is cold shock, with such differences: be sure to wet your neck thoroughly before entering the water very gradually.
Two culprits: the mistral and the tramontane
The cause of this phenomenon is the wind, or rather the winds, namely the mistral and the tramontane, which have been blowing continuously since the beginning of the week. Before the tramontane set in on Sunday evening, the water temperature in Sète was still 23°C (73°F): it dropped by 5°C (9°F) in just two days! Chills guaranteed…
« This weekend, the flow will shift to the south, and then the sea breezes will take over: the wind will blow from the sea towards the land, bringing warm waters back to the beach, which will raise the water temperature.«
These winds cause what is known as upwelling: they push warm waters offshore, which are then replaced by much cooler waters rapidly rising from the depths near the shore. The steeper the slope of the shore, the more the waters will come from deep areas and, therefore, will be colder.
While the sky is often blue near the Mediterranean in summer, bathing conditions can vary greatly from one region to another. On the other hand, it is estimated that beyond a few dozen meters depth, the waters of seas and oceans maintain a constant temperature throughout the year. This difference disappears in the open sea.
Mistral and tramontane will weaken this afternoon, gusting to just 40 km/h, before ceasing tomorrow. Sea breezes will then take over, as the flow recovers to the south this weekend. As the wind blows from the sea towards the land, it will bring the warm waters towards the beaches, and water temperatures will gradually rise.
Source: Tametéo
