Enhanced Arctic sea ice melting controlled by larger heat discharge of mid-Holocene rivers

Abstract

Arctic sea ice retreat is linked to extrapolar thermal energy import, while the potential impact of pan-Arctic river heat discharge on sea-ice loss has been unresolved. We reconstructed the Holocene history of Arctic sea ice and Russian pan-Arctic river heat discharge, combining ice-rafted debris records and sedimentation rates from the East Siberian Arctic Shelf with a compilation of published paleoclimate and observational data. In the mid-Holocene, the early summer (June–July) solar insolation was higher than that during the late Holocene, which led to a larger heat discharge of the Russian pan-Arctic rivers and contributed to more Arctic sea ice retreat. This intensified decline of early-summer sea ice accelerated the melting of sea ice throughout the summertime by lowering regional albedos. Our findings highlight the important impact of the larger heat discharge of pan-Arctic rivers, which can reinforce Arctic sea-ice loss in the summer in the context of global warming.

Climate and ice conditions of East Siberian Sea during Holocene: Reconstructions based on sedimentary geochemical multiproxy

“…Taking note of the sea level change curve (Figure 3) and paleogeographic reconstructions for this period (Figure 1), we can conclude that sediments of layer 1 accumulated in the semi-closed estuary of paleo-Indigirka. It is confirmed by a low bromine content indicates low water salinity (Astakhov et al, 2015; Mayer et al, 2007), and an anomalously high sedimentation rate (Dong et al, 2022).…”

“…Sediments of cores LV77-36-1 and LV77-36-2 are clayey silts, with a relatively small admixture of sand (0.5%–4.8%); they are notable for their slight variability along the core. In the LV77-36-1 core, the mean median size varies from 5.6 to 8.8 µm and continues to increase up to the top of the core (Dong et al, 2022). The finest-grained sediments with minimum admixture of sand accumulated up to 7000 years ago.…”

“…The finest-grained sediments with minimum admixture of sand accumulated up to 7000 years ago. In sediments accumulated after 5 ka that exhibited a general trend of increasing sand content and median diameter, interlayers with different silt/clay ratios alternated (Dong et al, 2022).…”

“…The age of the LV77-36-1 core was determined according to a age model developed based on calibrated AMS 14 C radiocarbon dates of mollusk shells (Dong et al, 2022). The age of the LV77-36-2 sediments was determined from the distribution of the non-equilibrium (atmospheric) 210 Pb isotope.…”

“…The chemical composition of core LV77-36-1 sediments was determined by the X-ray fluorescence method on the energy dispersion spectrometer ARL Quant’X, (Thermo Fisher) using SGH5, MAN, JH-1 standards and control analyzes by other methods (Astakhov et al, 2020) from discrete samples with an interval of 1–2 cm (Figure 3, Supplemental Table SD4, available online). The upper 150 cm of the core (5.5 ka) was characterized by a low sedimentation rate (Dong et al, 2022) and analyzed with a step of 1 cm; however, the lower 150 cm of the core exhibited a step of 2 cm. Other sediment characteristics (grain size, TOC, and opal), total diatom content, and diatom assemblages were studied using a method in the literature (Astakhov et al, 2020; Tsoy et al, 2017) with a step of 2–4 cm.…”