Simulating Impacts of Precipitation on Ice Cover and Surface Water Temperature Across Large Lakes

Precipitation impacts on ice cover and water temperature in the Laurentian Great Lakes were examined using state‐of‐the‐art coupled ice‐hydrodynamic models. Numerical experiments were conducted for the recent anomalously cold (2014–2015) and warm (2015–2016) winters that were accompanied by high and low ice coverage over the lakes, respectively. The results of numerical experiments showed that snow cover on the ice, which is the manifestation of winter precipitation, reduced the total ice volume (or mean ice thickness) in all of the Great Lakes, shortened the ice duration, and allowed earlier warming of water surface. The reduced ice volume was due to the thermal insulation of snow cover. The surface albedo was also increased by snow cover, but its impact on the delay the melting of ice was overcome by the thermal insulation effect. During major snowstorms, snowfall over the open lake caused notable cooling of the water surface due to latent heat absorption. Overall, the sensible heat flux from rain in spring and summer was found to have negligible impacts on the water surface temperature. Although uncertainties remain in overlake precipitation estimates and model’s representation of snow on the ice, this study demonstrated that winter precipitation, particularly snowfall on the ice and water surfaces, is an important contributing factor in Great Lakes ice production and thermal conditions from late fall to spring.Plain Language SummarySnow and rain impact on ice cover and water temperature in large lakes were studied using a computational model for an example of the Laurentian Great Lakes. It was found that snow cover increased the reflection of solar radiation but at the same time prevented lake ice from the growing, resulting in less formation of ice and slightly earlier melting. The earlier ice melting also allowed earlier warming of the water surface in spring. Major snowstorms caused slight cooling in the water surface temperature because snowflakes absorbed heat when it touched the water surface to melt. On the other hand, warmer rain barely changed the water surface temperature during summer.Key PointsPrecipitation impacts on Great Lakes ice cover and water temperature were evaluated using a coupled ice‐hydrodynamic modelThe model results showed that snow cover on the ice reduced the net production of ice, which resulted in earlier decay of ice coverThe model results showed that snowfall cooled the water surface notably through latent heat absorption during stormsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155461/1/jgrc23973.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155461/2/jgrc23973_am.pd

Evaluating and improving modeled turbulent heat fluxes across the North American Great Lakes

Turbulent fluxes of latent and sensible heat are important physical processes that influence the energy and water budgets of the North American Great Lakes. These fluxes can be measured in situ using eddy covariance techniques and are regularly included as a component of lake–atmosphere models. To help ensure accurate projections of lake temperature, circulation, and regional meteorology, we validated the output of five algorithms used in three popular models to calculate surface heat fluxes: the Finite Volume Community Ocean Model (FVCOM, with three different options for heat flux algorithm), the Weather Research and Forecasting (WRF) model, and the Large Lake Thermodynamic Model. These models are used in research and operational environments and concentrate on different aspects of the Great Lakes' physical system. We isolated only the code for the heat flux algorithms from each model and drove them using meteorological data from four over-lake stations within the Great Lakes Evaporation Network (GLEN), where eddy covariance measurements were also made, enabling co-located comparison. All algorithms reasonably reproduced the seasonal cycle of the turbulent heat fluxes, but all of the algorithms except for the Coupled Ocean–Atmosphere Response Experiment (COARE) algorithm showed notable overestimation of the fluxes in fall and winter. Overall, COARE had the best agreement with eddy covariance measurements. The four algorithms other than COARE were altered by updating the parameterization of roughness length scales for air temperature and humidity to match those used in COARE, yielding improved agreement between modeled and observed sensible and latent heat fluxes.</p

The Changing Face of Winter: Lessons and Questions From the Laurentian Great Lakes

Among its many impacts, climate warming is leading to increasing winter air temperatures, decreasing ice cover extent, and changing winter precipitation patterns over the Laurentian Great Lakes and their watershed. Understanding and predicting the consequences of these changes is impeded by a shortage of winter-period studies on most aspects of Great Lake limnology. In this review, we summarize what is known about the Great Lakes during their 3–6 months of winter and identify key open questions about the physics, chemistry, and biology of the Laurentian Great Lakes and other large, seasonally frozen lakes. Existing studies show that winter conditions have important effects on physical, biogeochemical, and biological processes, not only during winter but in subsequent seasons as well. Ice cover, the extent of which fluctuates dramatically among years and the five lakes, emerges as a key variable that controls many aspects of the functioning of the Great Lakes ecosystem. Studies on the properties and formation of Great Lakes ice, its effect on vertical and horizontal mixing, light conditions, and biota, along with winter measurements of fundamental state and rate parameters in the lakes and their watersheds are needed to close the winter knowledge gap. Overcoming the formidable logistical challenges of winter research on these large and dynamic ecosystems may require investment in new, specialized research infrastructure. Perhaps more importantly, it will demand broader recognition of the value of such work and collaboration between physicists, geochemists, and biologists working on the world\u27s seasonally freezing lakes and seas

Global lake responses to climate change

Climate change is one of the most severe threats to global lake ecosystems. Lake surface conditions, such as ice cover, surface temperature, evaporation and water level, respond dramatically to this threat, as observed in recent decades. In this Review, we discuss physical lake variables and their responses to climate change. Decreases in winter ice cover and increases in lake surface temperature modify lake mixing regimes and accelerate lake evaporation. Where not balanced by increased mean precipitation or inflow, higher evaporation rates will favour a decrease in lake level and surface water extent. Together with increases in extreme-precipitation events, these lake responses will impact lake ecosystems, changing water quantity and quality, food provisioning, recreational opportunities and transportation. Future research opportunities, including enhanced observation of lake variables from space (particularly for small water bodies), improved in situ lake monitoring and the development of advanced modelling techniques to predict lake processes, will improve our global understanding of lake responses to a changing climate

Simulating Impacts of Precipitation on Ice Cover and Surface Water Temperature Across Large Lakes

Precipitation impacts on ice cover and water temperature in the Laurentian Great Lakes were examined using state‐of‐the‐art coupled ice‐hydrodynamic models. Numerical experiments were conducted for the recent anomalously cold (2014–2015) and warm (2015–2016) winters that were accompanied by high and low ice coverage over the lakes, respectively. The results of numerical experiments showed that snow cover on the ice, which is the manifestation of winter precipitation, reduced the total ice volume (or mean ice thickness) in all of the Great Lakes, shortened the ice duration, and allowed earlier warming of water surface. The reduced ice volume was due to the thermal insulation of snow cover. The surface albedo was also increased by snow cover, but its impact on the delay the melting of ice was overcome by the thermal insulation effect. During major snowstorms, snowfall over the open lake caused notable cooling of the water surface due to latent heat absorption. Overall, the sensible heat flux from rain in spring and summer was found to have negligible impacts on the water surface temperature. Although uncertainties remain in overlake precipitation estimates and model’s representation of snow on the ice, this study demonstrated that winter precipitation, particularly snowfall on the ice and water surfaces, is an important contributing factor in Great Lakes ice production and thermal conditions from late fall to spring.Plain Language SummarySnow and rain impact on ice cover and water temperature in large lakes were studied using a computational model for an example of the Laurentian Great Lakes. It was found that snow cover increased the reflection of solar radiation but at the same time prevented lake ice from the growing, resulting in less formation of ice and slightly earlier melting. The earlier ice melting also allowed earlier warming of the water surface in spring. Major snowstorms caused slight cooling in the water surface temperature because snowflakes absorbed heat when it touched the water surface to melt. On the other hand, warmer rain barely changed the water surface temperature during summer.Key PointsPrecipitation impacts on Great Lakes ice cover and water temperature were evaluated using a coupled ice‐hydrodynamic modelThe model results showed that snow cover on the ice reduced the net production of ice, which resulted in earlier decay of ice coverThe model results showed that snowfall cooled the water surface notably through latent heat absorption during stormsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155461/1/jgrc23973.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155461/2/jgrc23973_am.pd

Ice Forecasting in the Next-Generation Great Lakes Operational Forecast System (GLOFS)

Ice Cover in the Great Lakes has significant impacts on regional weather, economy, lake ecology, and human safety. However, forecast guidance for the lakes is largely focused on the ice-free season and associated state variables (currents, water temperatures, etc.) A coupled lake-ice model is proposed with potential to provide valuable information to stakeholders and society at large about the current and near-future state of Great Lakes Ice. The model is run for three of the five Great Lakes for prior years and the modeled ice cover is compared to observations via several skill metrics. Model hindcasts of ice conditions reveal reasonable simulation of year-to-year variability of ice extent, ice season duration, and spatial distribution, though some years appear to be prone to higher error. This modeling framework will serve as the basis for NOAA&rsquo;s next-generation Great Lakes Operational Forecast System (GLOFS); a set of 3-D lake circulation forecast modeling systems which provides forecast guidance out to 120 h

The Changing Face of Winter: Lessons and Questions From the Laurentian Great Lakes

Among its many impacts, climate warming is leading to increasing winter air temperatures, decreasing ice cover extent, and changing winter precipitation patterns over the Laurentian Great Lakes and their watershed. Understanding and predicting the consequences of these changes is impeded by a shortage of winter- period studies on most aspects of Great Lake limnology. In this review, we summarize what is known about the Great Lakes during their 3- 6 months of winter and identify key open questions about the physics, chemistry, and biology of the Laurentian Great Lakes and other large, seasonally frozen lakes. Existing studies show that winter conditions have important effects on physical, biogeochemical, and biological processes, not only during winter but in subsequent seasons as well. Ice cover, the extent of which fluctuates dramatically among years and the five lakes, emerges as a key variable that controls many aspects of the functioning of the Great Lakes ecosystem. Studies on the properties and formation of Great Lakes ice, its effect on vertical and horizontal mixing, light conditions, and biota, along with winter measurements of fundamental state and rate parameters in the lakes and their watersheds are needed to close the winter knowledge gap. Overcoming the formidable logistical challenges of winter research on these large and dynamic ecosystems may require investment in new, specialized research infrastructure. Perhaps more importantly, it will demand broader recognition of the value of such work and collaboration between physicists, geochemists, and biologists working on the world’s seasonally freezing lakes and seas.Plain Language SummaryThe Laurentian Great Lakes are the world’s largest freshwater ecosystem and provide diverse ecosystem services to millions of people. Affected by multiple interacting stressors, this system is the target of extensive restoration and management efforts that demand robust scientific knowledge. Winter limnology represents a key knowledge gap that limits understanding and prediction of the function of the Great Lakes and other large temperate lakes. Here, we summarize what is known about the Great Lakes during their 3- 6 months of winter, identify key questions that must be addressed to improve understanding of the physical, chemical, and biological functioning of large lakes in winter, and suggest ways to address these questions. We show that ice cover is a - master variable- that controls numerous aspects of large temperate lake ecology and that the effects of the ongoing reduction in ice cover extent and duration cannot be predicted without improved knowledge of winter limnology.Key PointsWinter limnology is a key knowledge gap that limits understanding and management of the Great Lakes and other large, seasonally frozen lakesWe review the winter physics, chemistry, and biology of the Great Lakes and identify priority questions for winter research on large lakesIce cover is a - master variable- for many large lake limnological processes, making a better understanding of its role a research priorityPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/168250/1/jgrg21922_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168250/2/jgrg21922.pd