The trade winds
Although Mauritius has two seasons, one meteorological phenomenon persists all year round, with varying degrees of intensity: the trade winds. This term is generally used in the plural, the trade winds, to designate a set of winds generated by the circulation of air between the major anticyclonic action centers of the subtropical regions and the intertropical convergence zone forming a vast low-pressure belt surrounding the planet. In Mauritius, the oceanic trade winds are naturally slowed by friction with the sea surface. Blowing quietly from the east, they are characterized by moderate and little-variable speeds, of the order of 20 km/h. They help to "cool" the air during the austral summer, particularly on the east and south coasts. The more sheltered west coast is less affected by the trade winds. In addition to lowering temperatures, these near-constant winds make sailing, windsurfing and kitesurfing ideal conditions.
Cyclones
Real climatic monsters with destructive power, cyclones sweep across the intertropical zone of the southern hemisphere during the austral summer, from November to April (in Mauritius, generally from January to March). They form in the south-western Indian Ocean, where sea temperatures exceed 26.5°C at the surface and up to 50 meters below the surface. These vortex depressions, which generally last no more than a week, measure between 300 and 1,000 km in diameter. At the center, in the famous "eye of the cyclone", calm reigns, while on the periphery, extremely violent winds blow. For a depression to be declared a tropical cyclone, the average wind speed must be at least 64 knots (118 km/h). It is this notion of speed that enables cyclones to be classified into 6 categories (a classification specific to the Indian Ocean): DT (Tropical Depression) - TTM (Moderate Tropical Storm) - FTT (Strong Tropical Storm) - CT (Tropical Cyclone) - CTI (Intense Tropical Cyclone) - CTTI (Very Intense Tropical Cyclone). Because of its small size, Mauritius is fortunately not often hit by these furious winds, but it has been dramatically affected by some of them in the past. Every year, around ten cyclones pass close to the island. Cyclone Carol in 1960 was the most devastating cyclone to hit Mauritius in recent decades, with winds in excess of 240 km/h and heavy rainfall. 42 deaths, some 1,700 injured, 80,000 homeless, an island ravaged: the toll was heavy and the event left a lasting impression.
The name of the cyclones
Each region of the globe where cyclones form has the opportunity to give this climatic event a name. In the southwest Indian Ocean, tropical low-pressure systems are given names when they reach the TTM (Moderate Tropical Storm) stage. These names, in fact given names, are drawn from a list compiled by the 15 member countries of the South-West Indian Ocean Tropical Cyclone Committee, and offer as balanced a mix as possible of first names from different countries, most of them in southern Africa. Until the 1999/2000 season, the names were exclusively feminine... Over the past 20 years, they have become mixed, alternating between masculine and feminine.
Climate change
It's impossible to predict the full extent and consequences of global climate change, especially if we do nothing to reverse the warming curve. What is certain, based on the average temperatures observed in recent years, is that this change is underway, and that its consequences could be dramatic for Mauritius. Like all the islands, Mauritius is likely to be affected first and foremost by rising sea levels. The relatively high altitude of its central plateau would protect a large part of the island and its inhabitants. But a rise in water levels of 50 centimetres before the end of the century (minimum forecast) would simply wipe out certain beaches, particularly on the west coast, increasing coastal erosion and threatening many homes. And if the rise in water levels were to accelerate, the archipelagos of Saint-Brandon and Agaléga, whose highest points rise only 2 meters above the ocean, as well as several islets surrounding Mauritius, would disappear altogether.
Threat to corals
Another threat to the coast and the island as a whole is the constant rise in ocean temperatures and acidification of the marine environment. Corals cannot withstand temperatures above 30°C for long. When seawater remains hot for several days, or even weeks, coral dies. To make matters worse, ocean acidification also contributes to coral mortality, as well as that of other marine organisms. Yet coral reefs are more than just ecological shelters for the most beautiful fish species. It also serves to protect coastlines by absorbing the energy of the swell and waves that break over this island in the middle of the ocean. Less coral also means more coastal erosion.
Other consequences
Another consequence of rising salt water levels is the possible "contamination" of clear drinking water. Water, the supply of which is a real problem in Mauritius, could run out in some places.
Global warming is also leading to an increase in the intensity of extreme weather phenomena. As cyclones derive their energy from the heat of water, the risk of them turning into super-powerful monsters increases with rising temperatures. In addition, longer periods of drought mean heavier rainfall. A long dry spell and the infiltration of salt water from the coast would be even more dramatic for Rodrigues, whose water resources depend entirely on rainwater and coastal drilling.
