Lake Ice Breakup Timing in the Lower Kuskokwim River Basin derived from Sentinel-2 Imagery over 2018-2023

Lake Ice Breakup Timing in the Lower Kuskokwim River Basin derived from Sentinel-2 Imagery over 2018-2023 Addison Pletcher1, Sarah Cooley1,2* and Eric Levenson1 1Department of Geography, University of Oregon, Eugene, OR, USA 2Division of Earth and Climate Sciences, Nicholas School of the Environment, Duke University, Durham, NC, USA *Contact: [e-mail] This dataset provides estimated lake ice breakup date each year from 2018 to 2023 derived from classification of Sentinel-2 optical satellite imagery for 145,955 lakes in the Lower Kuskokwim River Basin in Alaska. A full description of the methods used to derive this dataset can be found in Pletcher et al (submitted) (will be linked once paper is published). Variables in CSV Lake_ID: identifier for all lakes in study area Year: Year of breakup detection Latitude: Latitude of lake centroid Longitude: Longitude of lake centroid Area: Lake area from the ALPOD dataset (Levenson et al., 2025) in square meters B_Estimate_intpl: Estimated breakup date interpolated between the two closest cloud-free Sentinel-2 observations Uncertainty_halved: +/- the number of days between the breakup date and the nearest cloud-free Sentinel-2 observations spanning the breakup period. In other words, the period over which linear interpolation occurs for breakup date estimation. Lower_Bound: The last day of observable ice coverage >25% for a given lake Upper_Bound: The first day of observable ice coverage <25% for a given lake Zero_Degree_Date: The date the 31 days prior to which had an average air temperature of 0°C or higher; the date when daily mean air temperature crosses the 0°C threshold when smoothed over a 31 day period. Data derived from ERA5-Land reanalysis. Lag_Days: The difference (in days) between the zero degree date and the breakup date. Note: any repeated columns of the above with the suffix "_J" refers to the same data but in Julian days for ease of analysis.