Swimmers taking a dip in the sea will not find it as refreshing. 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 29°C and peaking up to 30.1°C 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 of the University of Malta elaborates 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 the sea temperatures change from place to place as well as in time, rising to highest values in late afternoon when the sea has accumulated the sun's radiation during the day, and cooling down by around 2°C 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 4th and Friday 5th August reached peaks of 28.6°C. 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 meter. 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 3m depth in a yacht marina on the eastern coast reached close to 31°C. The warm waters near Malta are in contrast to the relatively cooler patch of sea west of the islands.