Recent accelerated warming of the Laurentian Great Lakes: Physical drivers

Abstract

The primary drivers of the recent accelerated warming of the Laurentian Great Lakes from 1982 to 2012 are explored through observations, remote sensing, and regional climate model experiments. The study focuses on the abrupt warming from 1997 to 1998 as a proxy for the long‐term warming trend. The lake surface warming has been heterogeneous in both space and time, ranging from moderate warming in late spring over the southern lakes and shallow areas of the northern lakes to strong warming in mid‐summer over the northern, deep lake areas. The greatest lake warming between 1997 and 1998 occurs over the deepest areas of Lake Superior during mid‐summer, primarily arising from enhanced heat accumulation during the mild winter of 1997/1998 and amplified by greater incoming surface solar radiation and air temperature during the spring of 1998, according to model experiments. The mild winter condition, together with the increased solar radiation and air temperature during spring, causes an earlier onset of springtime stratification, resulting in enhanced heat absorption by surface water and thereby contributing to lake surface warming during the subsequent summer in 1998 compared with 1997. In contrast, the modest peak warming over southern lakes and shallow areas of northern lakes from 1997 to 1998 is a rapid response to synchronous increases in solar radiation and air temperature during May between the 2 yr. Changes in antecedent wintertime lake ice cover are found to have played only a minor role in the accelerated warming trend of the Laurentian Great Lakes.

On the predictability of lake surface temperature using air temperature in a changing climate: A case study for Lake Tahoe (U.S.A.)

“…This would allow one to directly simulate fundamental lake‐climate interactions, thus improving the simulation of both lake processes and regional climate. Recent attempts in this direction have been made to adopt one‐dimensional lake models (e.g., Goyette and Perroud, ; Zhong et al ; Sugiyama et al ), which however require an entire set of meteorological variables, causing a potentially larger propagation of uncertainties and errors typical of climate models. An example is given by the comparison between air2water (Piccolroaz et al ) and a coupled RCM‐lake model (Zhong et al ) for the case of Lake Superior (U.S.A.‐Canada), where the latter model is characterized by larger errors, with many cases being statistical significant.…”

Transparency, Geomorphology and Mixing Regime Explain Variability in Trends in Lake Temperature and Stratification across Northeastern North America (1975–2014)

“…In the future, LSWT warming rates may be more consistent with air temperature rates depending on future stabilization in air quality improvements [4,39]. Similarly, milder winters, shortening ice cover and less snow cover on ice occurring in NENA and around the northern latitudes [50,51] will all contribute to lowered lake albedo, earlier stratification and longer duration of energy absorption, resulting in intensified summer warming [11,12,52]. Changes in wind speed [53,54], water transparency [55,56] and hydrologic inflows [54] can all alter lake warming rates.…”

Amplified surface temperature response of cold, deep lakes to inter-annual air temperature variability

“…However, a direct cause and effect relationship of winter ice cover on summer LSWTs has yet to be reported, and its influence in driving excess summer LSWT warming is in question 21 . Moreover, other studies have demonstrated that ice cover is not a prerequisite for accelerated summer LSWT warming 12, 22 .…”