Abstract
Studies on the impact of climate change in lakes have mainly focused on the average response of lake surface temperature during three summer months (July, August, September, usually termed JAS). Focusing on the Laurentian Great Lakes, we challenge this common assumption by showing that the thermal behaviour is diversified in time both among different lakes and within a single one. Deep regions experience a stronger warming concentrated in early summer, mainly due to anticipated stratification, while shallow parts respond more uniformly throughout the year. To perform such analysis, we use the difference between the five warmest and coldest years in a series of 20 years as a proxy of possible effects of climate alterations, and compare the warming of lake surface temperature with that of air temperature. In this way, based on past observations obtained from satellite images, we show how the warming is heterogeneously distributed in time and in space, and that the quantification of lakes’ thermal response to climate change is chiefly influenced by the time window used in the analysis. Should we be more careful when considering averaged indicators of lake thermal response to climate change?
Highlights
Lakes are considered as ‘sentinels of climate change’ [1, 2], making the study of their thermal trends informative to gather insights on how inland water resources respond to evolving climate conditions [3–6]
We use the difference between the five warmest and coldest years in a series of 20 years as a proxy of possible effects of climate alterations, and compare the warming of lake surface temperature with that of air temperature. In this way, based on past observations obtained from satellite images, we show how the warming is heterogeneously distributed in time and in space, and that the quantification of lakes’ thermal response to climate change is influenced by the time window used in the analysis
Sensitivity to warming described by timeaveraged indicators We have seen that the lake thermal response is characterised by a complex temporal dynamics, so two fundamental questions arise: Can we describe the lake surface water temperature (LSWT) warming in a simplified way, for instance by means of time-averaged indicators? Which time window should be used for air temperature (AT) warming to properly quantify and predict its effect on LSWT in a given period? To address these questions, we refer to different time windows: the conventional July–August–September (JAS) period, which is typically considered in analyses of summer warming in lakes [10, 11, 17, 21, 31, 49], the period May– June–July (MJJ), the annual mean, and the single-month averages from April to September
Summary
Lakes are considered as ‘sentinels of climate change’ [1, 2], making the study of their thermal trends informative to gather insights on how inland water resources respond to evolving climate conditions [3–6]. Several significant works on this subject focused on the response of LSWT to AT during three summer months: July, August and September (JAS). The use of these three months (instead of other combinations or single representative months) to describe the summer period was originally proposed by Austin and Colman [7], and later presented with the acronym JAS by Schneider et al [8].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
