Sensitivity of lake thermal and mixing dynamics to climate change

Abstract

Warming-induced changes in lake thermal and mixing regimes present risks to water quality and ecosystem services provided by U.S. lakes and reservoirs. Modulation of responses by different physical and hydroclimatic settings are not well understood. We explore the potential effects of climate change on 27 lake "archetypes" representative of a range of lakes and reservoirs occurring throughout the U.S. Archetypes are based on different combinations of depth, surface area, and water clarity. LISSS, a one-dimensional dynamic thermal simulation model, is applied to assess lake response to multiple mid-21st century change scenarios applied to nine baseline climate series from different hydroclimatic regions of the U.S. Results show surface water temperature increases of about 77 % of increase in average air temperature change. Bottom temperature changes are less (around 30 %) for deep lakes and in regions that maintain mid-winter air temperatures below freezing. Significant decreases in length of ice cover are projected, and the extent and strength of stratification will increase throughout the U.S., with systematic differences associated with depth, surface area, and clarity. These projected responses suggest a range of future challenges that lake managers are likely to face. Changes in thermal and mixing dynamics suggest increased risk of summer Climatic Change (2015) 129:295-305

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

“…Secchi depth was positively correlated with mean depth (r = 0.57, p < 0.001). Therefore, we included a depth index (mean depth 1.5 /Secchi depth) that was independent of Secchi depth [19]. This depth index was not correlated with Secchi depth (r = 0.03, p = 0.62) and represents the effect of light penetration into water and resistance to mixing related to depth and independent of water clarity.…”

“…In the most extreme results we reviewed, six large lakes in California and Nevada showed surface warming at twice the rate of regional air temperature changes based on satellite imagery (1991-2008; [34]) relative to 50% faster in this study (Table 2). Air temperature trends alone underestimate LSWT in models of lake surface equilibrium temperature (e.g., [19,47] predict LSWT at 70-80% of air temperature warming rates), suggesting that such models may be missing key integrative factors.…”

“…These stratification trends reflect greater increases in surface water temperature relative to deeper waters. Additionally, warmer late winter and early spring air temperatures combined with earlier ice off and earlier stratification will increase thermocline stability over the course of the season, resulting in stronger peak stratification [19]. The strength of thermal stratification is increasing more rapidly in lakes of intermediate depth (Figure 6f) with larger heat budgets and more resistance to increases in total thermal content throughout the water column than smaller lakes [19].…”

“…The changes in thermal stratification patterns over time are likely to be highly variable across lakes. For example, effects of climate change on lake stratification varied with lake depth, surface area and water clarity in thermal simulation models [19] and varied with morphometry and average lake temperature in long-term monitoring records [16]. Changes in lake stratification patterns are also likely region-specific, since the strength of stratification is largely related to average lake temperature [16], which will vary with latitude.…”

Exceptional summer warming leads to contrasting outcomes for methane cycling in small Arctic lakes of Greenland

“…Currently, in the Arctic, small lakes (surface area < 10 km 2 ) are abundant (Downing, 2010;Downing et al, 2006) and emit substantially more CH 4 per unit area than larger lakes (Bastviken et al, 2004;Cole et al, 2007;Juutinen et al, 2009;Wik et al, 2016), and seasonal variability in CH 4 emissions are influenced by energy input and organic carbon availability (Tan et al, 2015). However, climate change will lead to variations in heat balance, temperature profiles, and vertical mixing in lakes (Jankowski et al, 2006;MacIntyre et al, 2009;Hinkel et al, 2012;Butcher et al, 2015), causing many variations to both lake structure (Livingstone 2003;Coats et al, 2006) and CH 4 dynamics. Microbial production of CH 4 by methanogens is dependent upon anoxia, temperature, and the amount and quality of organic carbon substrates (Liikanen et al, 2003;Kankaala et al, 2006;Duc et al, 2010;Borrel et al, 2011).…”