Comment on bg-2021-39

Abstract

Lakes act as important sinks for inorganic and organic sediment components. However, investigations of sedimentary carbon budgets within glacial lakes are currently absent from Arctic Siberia. The aim of this paper is to provide the first reconstruction of accumulation rates, sediment and carbon budgets from a lacustrine sediment 20 core from Lake Rauchuagytgyn, Chukotka (Arctic Siberia). We combined multiple sediment-biogeochemical and sedimentological parameters from a radiocarbon-dated 6.5 m sediment core with lake basin hydroacoustic data to derive sediment stratigraphy, sediment volumes, and infill budgets. Our results distinguished three principal sediment and carbon accumulation regimes that could be identified across all measured environmental proxies including Early MIS2 (ca. 29-23.4 cal. ka BP), Mid-to-late MIS2 (ca. 23.4-11.5 cal. ka BP), and Holocene (ca. 2511.5-present). Estimated organic carbon accumulation rates (OCARs) were higher within Holocene sediments (average 3.53 g OC m -2 a -1 ) than Pleistocene sediments (average 1.09 g OC m -2 a -1 ) and are similar to those calculated for boreal lakes from Quebec and Finland and Lake Baikal but significantly lower than Siberian thermokarst lakes and Alberta glacial lakes. Using a bootstrapping approach, we estimated the total organic carbon pool to 0.26 ± 0.02 Mt and a total sediment pool of 25.7 ± 1.71 Mt within a hydroacoustically derived 30 sediment volume of ca. 32990557 m 3 . The total organic carbon pool is substantially smaller than Alaskan Yedoma, thermokarst lake sediments, and Alberta glacial lakes but shares similarities with Finnish boreal lakes.Temporal variability in sediment and carbon accumulation dynamics at Lake Rauchuagytgyn is controlled predominantly by palaeoclimate variation that regulates lake ice-cover dynamics and catchment glacial, fluvial and permafrost processes through time. These processes, in turn, affect catchment and within-lake primary 35 productivity as well as catchment soil development. Spatial differences to other lake systems at a trans-regional scale likely relates to the high-latitude, mountainous location of Lake Rauchuagytgyn.