Increasing maximum lake surface temperature under climate change

Martin T Dokulil,Stephen C Maberly,Linda May,R Iestyn Woolway,Gesa A Weyhenmeyer,Elvira De Eyto

doi:10.1007/s10584-021-03085-1

Abstract

Annual maximum lake surface temperature influences ecosystem structure and function and, in particular, the rates of metabolic activities, species survival and biogeography. Here, we evaluated 50 years of observational data, from 1966 to 2015, for ten European lakes to quantify changes in the annual maximum surface temperature and the duration above a potentially critical temperature of 20 °C. Our results show that annual maximum lake surface temperature has increased at an average rate of +0.58 °C decade−1 (95% confidence interval 0.18), which is similar to the observed increase in annual maximum air temperature of +0.42 °C decade−1 (95% confidence interval 0.28) over the same period. Increments in lake maximum temperature among the ten lakes range from +0.1 in the west to +1.9 °C decade−1 in the east. Absolute maximum lake surface water temperatures were reached in Wörthersee, 27.5 °C, and Neusiedler See, 31.7 °C. Periods exceeding a critical temperature of 20 °C each year became two to six times longer than the respective average (6 to 93). The depth at which water temperature exceeded 20 °C increased from less than 1 to more than 6 m in Mondsee, Austria, over the 50 years studied. As a consequence, the habitable environment became increasingly restricted for many organisms that are adapted to historic conditions.

Highlights

Climate change is an essential feature of the Anthropocene (Steffen et al 2011; Keys et al 2019)
Long-term changes in mean lake surface water temperatures (LSWT) summarized for 19 European lakes by Arvola et al (2010) and globally by O’Reilly et al (2015) suggested an average summer increase of 0.34 °C decade−1 over recent decades
The minimum temperature increased coherently in several European lakes (Woolway et al 2019b) while changes in LSWTmax were reported for Austria and Poland (Dokulil 2018; Ptak et al 2019)

Summary

Introduction

Climate change is an essential feature of the Anthropocene (Steffen et al 2011; Keys et al 2019). Long-term changes in mean LSWT summarized for 19 European lakes by Arvola et al (2010) and globally by O’Reilly et al (2015) suggested an average summer increase of 0.34 °C decade−1 over recent decades. A specific analysis showed that climatic effects on lake minimum (LSWTmin) or maximum surface water temperature (LSWTmax) have, as single extreme values, much greater variability than average lake temperature, need a higher temporal resolution and are less often reported. The minimum temperature increased coherently in several European lakes (Woolway et al 2019b) while changes in LSWTmax were reported for Austria and Poland (Dokulil 2018; Ptak et al 2019). We analyse the changes and temporal development of LSWTmax from long-term in situ observations (50 years) in a suite of European lakes

Methods

Results

Discussion

Conclusion