Abstract
Abstract. The formation, growth, and decay of freshwater ice on lakes and rivers are fundamental processes of northern regions with wide-ranging implications for socio-ecological systems. Ice thickness at the end of winter is perhaps the best integration of cold-season weather and climate, while the duration of thick and growing ice cover is a useful indicator for the winter travel and recreation season. Both maximum ice thickness (MIT) and ice travel duration (ITD) can be estimated from temperature-driven ice growth curves fit to ice thickness observations. We simulated and analyzed ice growth curves based on ice thickness data collected from a range of observation programs throughout Alaska spanning the past 20–60 years to understand patterns and trends in lake and river ice. Results suggest reductions in MIT (thinning) in several northern, interior, and coastal regions of Alaska and overall greater interannual variability in rivers compared to lakes. Interior regions generally showed less variability in MIT and even slightly increasing trends in at least one river site. Average ITD ranged from 214 d in the northernmost lakes to 114 d across southernmost lakes, with significant decreases in duration for half of sites. River ITD showed low regional variability but high interannual variability, underscoring the challenges with predicting seasonally consistent river travel. Standardization and analysis of these ice observation data provide a comprehensive summary for understanding changes in winter climate and its impact on freshwater ice services.
Highlights
Arctic amplification is an enhanced warming response in high latitudes relative to increasing global temperature (Serreze and Barry, 2011)
Freshwater ice thickness and duration may function as robust integrators of winter climate, as they respond both to changes in air temperature and snow accumulation
Spatial patterns of maximum ice thickness (MIT) averaged over periods greater than two decades ranged from 67 cm in Southcentral (Anchorage) and 70 cm in the Interior (Fairbanks) to 167 cm on the Arctic Coastal Plain of northern Alaska (Utqiagvik) (Table 2)
Summary
Arctic amplification is an enhanced warming response in high latitudes relative to increasing global temperature (Serreze and Barry, 2011). Arp et al.: Patterns and trends in maximum ice thickness and safe travel duration tion on freshwater ice should be most evident in this northern coastal region where Alexeev et al (2016) demonstrated a linkage between sea ice extent and lake ice growth This long, yet intermittent, record of lake ice thickness in northern Alaska comes from a variety of observation efforts including community-based monitoring facilitated by government agencies (Bilello, 1980) and school science programs (Morris and Jeffries, 2010). Large data gaps in records make it difficult to ascertain trends at some long-term sites (Cherry, 2019) For these reasons, we are motivated to standardize ice thickness according to ice growth curves informed by field observations and calculate relevant metrics, maximum ice thickness (MIT) and ice travel duration (ITD), as well as to merge analyses of both river and lake ice in Alaska.
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