Sediment and carbon accumulation in a glacial lake in Chukotka (Arctic Siberia) during the late Pleistocene and Holocene: Combining hydroacoustic profiling and down-core analyses

Abstract

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 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. 11.5–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 sediment volume of ca. 32990557 m3. 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 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.

14,000-year Carbon Accumulation Dynamics in a Siberian Lake Reveal Catchment and Lake Productivity Changes

“…It is also possible that longer periods of ice cover compared to Unit 2 and Unit 3 restricted in situ autotrophic production (algae) in the lake. However, these TOC values are high compared to other reported values from Yedoma permafrost (Windirsch et al, 2020;Vyse et al, 2021; Figure 8). Moderately high δ 13 C values, high TIC values, and relatively low TOC (Figure 4) compared to Units 2 and 3 corroborate lower levels of bioproductivity within the lake and indicate input from sources of inorganic carbon during this time (Schirrmeister et al, 2011), as shown in other lake records from Yakutia (Biskaborn et al, 2012).…”

“…Unit 3 is more homogenous than Unit 1 and Unit 2, both in terms of a lack of discernable laminations or other features and homogeneity within the biogeochemical metrics analyzed. Average TOC content is >34 wt% (ranging from 29 to 39 wt%) in this unit, higher than elsewhere along the core and an order of magnitude above most of the reported values for lakes across Yedoma regions (Vyse et al, 2021). Presumably, this period heralded higher levels of bioproductivity and increased nutrient supply to an expanding lake at the study site.…”

“…Moreover, the inferred OCARs for Unit 1 indeed represent the lowest values of the whole sequence, with an average of ∼100 g OC m −2 a −1 (ranging from 63 to 158 g OC m −2 a −1 ; Figure 5). These low values are nevertheless higher than reported rates for temperate latitudes, such as the Great Lakes in North America (e.g., Meyers, 2003), and much higher than several arctic/subarctic sites, such as northern Québec (Ferland et al, 2012(Ferland et al, , 2014, Finland (Pajunen, 2000), Greenland (Anderson et al, 2009;Sobek et al, 2014), as well as southeastern and northeastern Siberia (Martin et al, 1998;Vyse et al, 2021).…”

“…This was the result of lower sedimentation (average MAR decreasing from ∼0.1 g cm −2 a −1 at the top of Unit 2 to ∼0.04 g cm −2 a −1 in the upper section of Unit 3). Still, OCAR values of 200 g OC m −2 a −1 are notably in the upper range of global modern values and significantly higher than elsewhere across high-latitude regions (Vyse et al, 2021;Figure 8). TIC remains consistently low throughout Unit 3, while δ 13 C increases in the lower half of the unit, before decreasing and then stabilizing in the upper half of the unit.…”

“…The TOC/TN atomic ratio at the bottom of the core represents the maximum (20) measured in the entire recovered sequence, indicating a stronger contribution of carbon produced by vascular land plants than aquatic algae (Figure 6) (Meyers, 1994). Both, the TOC (average 12 wt%) and TN (average 0.68 wt%) values are lower in Unit 1 compared to Unit 2 and Unit 3, although relatively high compared to other sites in this region (Vyse et al, 2021). Combined with moderate MAR values (average 0.09 g cm −2 a −1 ), this resulted in the lowest OCAR values (average 101 g OC m −2 a −1 ) for the whole core (Figure 2, Figure 5).…”