Figure 3: Increasing difference between surface water and air temperature (Tw-Ta) with increasing air temperature (Ta) in Lake Erken.

Shown are year-to-year variations during 1989 to 2015 of in situ Ta and Tw-Ta from Lake Erken at day 21 of each month at midnight (left panel) and noon (right panel). All relationships are linear and highly significant (p < 0.0001). The orange color indicates when there is an upward sensible heat flux and the blue color when there is a downward sensible heat flux.