Fig. 2: Surface and subsurface water temperature observations in Lake Michigan.

a Daily lake surface temperature from the GLSEA at the thermistor location. b Water temperature time-series at the 110 m depth transect. c, d A zoomed surface and subsurface temperature record for 2008–2009, equivalent to the period highlighted in gray in a and b, indicating the 110 m overturn date, “O”, minimum temperature/date, “M”, and stratification temperature/date, “S”.