Sea temperature soars beyond 30°C

If you went for a swim over the weekend and found the water not to be as refreshing as you might have expected, it was because the sea temperature has soared beyond 30ºC, according to the Physical Oceanography Research Group at the University of Malta.

Coordinator Aldo Drago said the intense solar radiation associated with the high air temperatures in recent days has naturally also affected the sea temperature.

Sea surface temperature (SST) has been on the high all around the Maltese Islands, reaching values well beyond 29ºC and peaking at 30.1ºC in the coastal stretch of sea opposite Marsascala on Saturday, 5 August, in the early evening hours.

SST is regularly monitored by orbiting satellites which keep an eye on its variability in time and in space.

The Physical Oceanography Research Group at the Department of Geosciences at the University of Malta elaborates on such data which provide snapshots of SST centred around midnight each day. Numerical models further produce maps of SST around the Maltese Islands as it changes during the day. These maps show how sea temperatures change from place to place as well as in time, rising to the highest values in the late afternoon when the sea has accumulated the sun’s radiation during the day, and cooling down by around 2ºC during the night, when the sea surface re-radiates part of its acquired heat energy back to the atmosphere.

The satellite SST for the night between Thursday 4 and Friday 5 August reached peaks of 28.6ºC. The sea continued to absorb heat energy during the day as solar radiation fluxes, measured by the heat station at the University of Malta, poured on land and at sea at persisting rates of up to 875 Watts per square metre.

The picture shows the modelled SST map of the sea on Saturday in the early evening hours when sea water temperatures reached their highest. Sea temperatures in shallower areas, ports, embayments and beaches were even higher. The sea temperature measured at a depth of 3 metres in a yacht marina on the eastern coast reached close to 31ºC. The warm waters near Malta are in contrast to the relatively cooler patch of sea west of the islands.

Sea Surface Temperature around the Maltese Islands at 5.30pm on 5 August reached a maximum of 30.1ºC on the eastern coast

The exceptional warming of the sea is in sharp contrast with the much cooler daily average temperatures registered in Delimara in the period 1977–2006 by the Malta Meteorological Office. The highest sea temperatures are typically reached in early August each year, but are 2ºC cooler than the recent values. The mean sea surface temperature in the coastal waters of the Maltese Islands has been steadily increasing at a hefty average rate of close to 0.05ºC per year since the late 1970s.