Overwintering Temperature and specific conductance data from Toolik Lake, North Slope, Alaska. 2023-2024

Lakes are abundant in the terrestrial arctic, extending over about one quarter of the territory. For approximately nine months of the year, the waters of arctic lakes are under ice. Despite the duration of the ice-covered period, few studies have addressed the limnology (biological, chemical, and physical features) of these lakes during winter and how conditions under ice effect the stratification and ecology of lakes during the summer. We evaluate the full year cycle of stratification and circulation in order to quantify the effects of hydrodynamics on nutrient and gas fluxes and place the results within the context of climate change in the Arctic. The goals of our study include: (1) quantifying physical and biogeochemical controls on under ice thermal structure and circulation, the flowpath of snow melt, and mixing during spring and fall (2) quantifying respiration rates in arctic lakes of differing morphology and on geological substrates (3) illustrating the linkages and feedbacks between these physical and biogeochemical processes, (4) linking temperature under the ice in winter to temperatures in the lakes in summer (5) quantifying rates of drawdown of oxygen (6) and evaluating the consequences of cryoconcentration on density structure and circulation under the ice. Our research has been being conducted in lakes studied by the Arctic Long Term Ecological Research (ARC LTER). The selected lakes are: Toolik Lake, Lake E1, Lake E5, Lake E6 and Lake N2. The lakes range in size from 1 to 1500 hectares. We measured temperature and bio-geochemical lake parameters in two different formats: time series, and profile data. Time series of water temperatures, specific conductance, pressure, and dissolved oxygen at several depths were obtained from a taut-line mooring in different seasons (summer and winter) across multiple years (between fall 2012 and fall 2016) We measured profiles of temperature and bio-geochemical lake parameters at the deepest site (and occasionally other sites) in all lakes during the same time as the time series. Efforts have been continued on Toolik Lake since 2016. Much of the previous data has been archived. The data here are the overwintering temperature and specific conductance data from 2023-2024.