September sea temperature hits 30-year record warmth

TALLINN - The record-breaking daily air temperatures in September have impacted the sea surface temperature along Estonia's coast, making it the warmest in the past 30 years.

The Tallinn University of Technology's (TalTech) climate service at the department of marine systems, which uses real-time satellite image analysis, shows that the sea surface temperature across Estonia's coastal waters is consistently around 17-18 degrees.

This is confirmed by data from coastal monitoring stations, indicating that the water temperature is significantly higher than the average for September over the last 30 years. Normally, the mid-September average sea temperature, depending on location, is around 14-15 degrees.

Since Aug. 29, a marine heatwave has developed in the eastern Baltic Sea. The peak of this heatwave occurred on Sept. 10, when water temperatures rose four degrees above normal, reaching 19-20 degrees, and the heatwave spanned 230,000 square kilometers of the Baltic Sea, covering over 50 percent of the area.

As of Tuesday, the affected area has shrunk to 80,000 square kilometers. Weather models for the coming days suggest that warm conditions will persist, indicating the marine heatwave may continue, making the water still suitable for swimming for those accustomed to cooler temperatures.

Rivo Uiboupin, associate professor of remote sensing at TalTech's department of marine systems, said that marine heatwaves are extreme conditions where water temperatures remain significantly higher for at least five days compared to the 30-year average for that time.

"Marine heatwaves are usually observed in the summer when absolute temperatures are highest, but they can also occur in fall or even winter if water temperatures are well above the long-term average," Uiboupin explained.

The frequency, duration, and extent of marine heatwaves in the Baltic Sea have increased over recent decades.

"What makes the current heatwave particularly interesting is that it has broken the intensity record for September marine heatwaves over the past 30 years," Uiboupin added.

This marine heatwave monitoring service relies on remote sensing data from the Copernicus Marine Service at the Copernicus marine environment monitoring service for the Baltic Sea and contributes to Estonia's efforts to adapt to climate change.