Thermal regimes of Rocky Mountain lakes warm with climate change

Abstract

Anthropogenic climate change is causing a wide range of stresses in aquatic ecosystems, primarily through warming thermal conditions. Lakes, in response to these changes, are experiencing increases in both summer temperatures and ice-free days. We used continuous records of lake surface temperature and air temperature to create statistical models of daily mean lake surface temperature to assess thermal changes in mountain lakes. These models were combined with downscaled climate projections to predict future thermal conditions for 27 high-elevation lakes in the southern Rocky Mountains. The models predict a 0.25°C·decade-1 increase in mean annual lake surface temperature through the 2080s, which is greater than warming rates of streams in this region. Most striking is that on average, ice-free days are predicted to increase by 5.9 days ·decade-1, and summer mean lake surface temperature is predicted to increase by 0.47°C·decade-1. Both could profoundly alter the length of the growing season and potentially change the structure and function of mountain lake ecosystems. These results highlight the changes expected of mountain lakes and stress the importance of incorporating climate-related adaptive strategies in the development of resource management plans.

Headwater lakes and their influence on downstream discharge

“…For example, headwater lakes can moderate the influence of forest harvesting on downstream thermal regimes, suggesting that catchments with lakes may be more resilient to forest cover disturbance than those without (Mellina et al ). In contrast, lake thermal regimes may be more responsive to climate warming than streams (Roberts et al ), which suggests that thermal regimes of catchments with lakes may be more sensitive to climate change than those without. In addition, the structure of the lake–stream network, the number of lakes present, and the characteristics of those lakes may all have a critical influence on how a catchment responds to environmental change (Epstein et al ; Spence et al ).…”

Effects of Climatic Change on Temperature and Thermal Structure of a Mountain Reservoir

“…Warming of the Lake Dillon mixed layer, 0.76 °C/decade, greatly exceeded mean warming rates for lakes in general: 0.34 °C (O'Reilly et al, ), 0.52 °C (Richardson et al, ), 0.20 °C (Schneider & Hook, ), projected surface warming of small montane lakes in Colorado (Roberts et al, , 0.47 °C) and a global group of large, deep lakes (Kraemer et al, , 0.20 °C). Warming of Lake Dillon is correlated with regional warming of air temperature (Mast et al, ), which is an expected covariant of (O'Reilly et al, ; Winslow et al, ; Woolway & Merchant, ), but not directly responsible for (Fink et al, ), warming of lakes.…”

“…Secular warming of air temperatures in the southern Rockies (0.45–0.93 °C/decade, Mast et al, ) is consistent with the warming of Lake Dillon surface water (0.70 °C/decade). Also, small montane lakes in Colorado presently are warming at the surface, as shown by satellite image imagery, at a rate of ~0.47 °C/decade (Roberts et al, ). The consequences of climatic warming for lake water column temperatures, however, cannot be determined accurately from changes in air temperatures or water surface temperatures.…”

Estimating lake–climate responses from sparse data: An application to high elevation lakes

“…The median area of the Rawah lakes was very similar to those for the other 590 lakes in the overall dataset. Agency data were included if the lake was: (1) natural, (2) located above 2100 m, and (3) temperature values were indicative of ice‐free conditions (≥ 4°C; Wetzel ; Roberts et al ). Depth at samples were not available for agency measurements, but were all regarded as “surface” temperatures.…”

“…Global distribution of high elevation lakes in published studies of lake warming, and their characteristics from Roberts et al () (a), O'Reilly et al () (b), Kirillin et al () (c), and Zhang et al () (d).…”