Baltic Sea surface temperatures may have reached 24°C 7,200 years ago compared to the current 12.7°C.
A new study (Weiss et al., 2022) indicates Baltic Sea regional surface temperatures ranged between 21-24°C from ~5.7 to 7.7 ka (thousand years ago). This period is referred to as the Baltic’s Holocene Thermal Maximum.
Temperatures dipped to 17.2°C at 1.373 ka. (The time span ranging from 0.0 ka to 3 ka is referred to in the study as the Modern Baltic, or M.B.)
The current (0.0 ka) surface temperature for the Baltic S is 12.7°C. This temperature is more than 11°C colder than the Baltic’s temperatures at 7.2 ka.
Image Source: Weiss et al., 2022
The magnitude of the Holocene Thermal Maximum warmth relative to today has also been reported for the Baltic Sea subsurface. Bottom water temperatures were approximately 9 to 13°C warmer (~16-20°C) than they are today (~7°C) from about 7,200 to 7,400 years ago (Ni et al., 2020).