Drivers and projections of ice phenology in mountain lakes in the western United States

Abstract

Climate change is causing rapid warming and altered precipitation patterns in mountain watersheds, both of which influence the timing of ice breakup in mountain lakes. To enable predictions of ice breakup in the future, we analyzed a dataset of mountain lake ice breakup dates derived from remote sensing and historical downscaled climate data. We evaluated drivers of ice breakup, constructed a predictive statistical model, and developed projections of mountain lake ice breakup date with global climate models. Using Random Forest analysis, we determined that winter and spring cumulative snow fraction (portion of precipitation falling as snow) and air temperature are the strongest predictors of ice breakup on mountain lakes. Interactions between precipitation, cumulative winter air temperature and lake surface area indicate that shifts in air temperature and precipitation affect smaller lakes (< 2 km 2) more than larger lakes (> 2-10 km 2). A linear mixed effects model (RMSE of 18 d), applied with an ensemble of 15 global climate models, projected that end-of-century ice breakup in mountain lakes will be earlier by 25 AE 4 and 61 AE 5 (mean AE SE) days for representative concentration pathways 4.5 and 8.5, respectively.

Winter Climate and Lake Morphology Control Ice Phenology and Under‐Ice Temperature and Oxygen Regimes in Mountain Lakes

“…Small lakes dominate the global distribution (<1 km 2 surface area; Downing et al., 2006), and midlatitude lakes are at greatest risk of ice loss as air temperature rises (Sharma et al., 2019), but climate change impacts on ice cover have been monitored mostly in large lakes at high latitudes (Magnuson et al., 2000; Sharma et al., 2019). Lakes that develop seasonal ice cover despite moderate winter air temperatures, such as mountain lakes in the western US, may be subject to declining trends in ice cover and shifts in associated processes (Caldwell et al., 2020; Sadro et al., 2018a), yet they remain under‐studied due to their inaccessibility and small size. Mountain landscapes contain heterogeneous topography and microclimates that mediate the expression of climate forcing (Novikmec et al., 2013; Sadro et al., 2018a), complicating efforts to predict lake responses at regional scales in these systems.…”

“…In mid‐latitude mountain ranges snowfall varies considerably among years, generating large inter‐annual differences in lake ice thickness and under‐ice conditions (Granados et al., 2020; Smits et al., 2020). A heavy snowpack melts later, delays ice‐off (Caldwell et al., 2020; Preston et al., 2016; Sadro et al., 2018a), and is associated with greater oxygen depletion under ice (Granados et al., 2020; Obertegger et al., 2017). However, general understanding of winter limnology in snow‐dominated mountain lakes, including drivers of temporal and spatial variation, is lacking.…”

Temporal dynamics of dissolved organic matter (DOM) in mountain lakes: the role of catchment characteristics

“…Following this pulse, fDOM decreased in the first phase, likely due to a combination of consumption by heterotrophic bacteria (Sadro et al 2011a, b) and photodegradation (Cory et al 2014). Because substantial snowmelt precedes ice breakup on mountain lakes (Caldwell et al 2021), large quantities of DOM can be delivered before lakes become ice free (Cortes et al 2017). Although we deployed sensors within a week of ice off, we may have missed the initial increase in DOM to a spring peak.…”

Climate Change is Contributing to Faster Rates of Lake Ice Loss in Lakes Around the Northern Hemisphere

“…Multiple drivers have been associated with ice phenology, including local weather conditions, teleconnection patterns, sunspot cycles, solar radiation, precipitation, volcanic eruptions, and climate change (Caldwell, Chandra, Feher, et al., 2020; Livingstone, 2000, 2003; Schmidt et al., 2019; Sharma & Magnuson, 2014). Warming air temperature has often been shown to be the strongest predictor of changes in lake ice phenology across the Northern Hemisphere (Filazzola et al., 2020; Korhonen, 2006; Sharma et al., 2019; Weyhenmeyer et al., 2004), although solar radiation, snow cover, and wind are also important drivers of lake ice phenology (Brown & Duguay, 2010; Caldwell, Chandra, Albright, et al., 2020; Filazzola et al., 2020; Kirillin et al., 2012). In fact, solar radiation is one of the primary drivers of lake ice thaw and is affected in part by the transparency of ice, albedo of the snow layer on the ice, and latitude (Caldwell, Chandra, Albright, et al., 2020; Kirillin et al., 2012).…”

“…Warming air temperature has often been shown to be the strongest predictor of changes in lake ice phenology across the Northern Hemisphere (Filazzola et al., 2020; Korhonen, 2006; Sharma et al., 2019; Weyhenmeyer et al., 2004), although solar radiation, snow cover, and wind are also important drivers of lake ice phenology (Brown & Duguay, 2010; Caldwell, Chandra, Albright, et al., 2020; Filazzola et al., 2020; Kirillin et al., 2012). In fact, solar radiation is one of the primary drivers of lake ice thaw and is affected in part by the transparency of ice, albedo of the snow layer on the ice, and latitude (Caldwell, Chandra, Albright, et al., 2020; Kirillin et al., 2012). Along the shoreline at shallow depths, solar radiation inputs and strong wind events commence the process of ice melt (Kirillin et al., 2012).…”