Holocene variability in sea ice cover, primary production, and Pacific‐Water inflow and climate change in the Chukchi and East Siberian Seas (Arctic Ocean)

Abstract

In this study, we present new detailed biomarker‐based sea ice records from two sediment cores recovered in the Chukchi Sea and the East Siberian Sea. These new biomarker data may provide new insights on processes controlling recent and past sea ice changes. The biomarker proxy records show (i) minimum sea ice extent during the Early Holocene, (ii) a prominent Mid‐Holocene short‐term high‐amplitude variability in sea ice, primary production and Pacific‐Water inflow, and (iii) significantly increased sea ice extent during the last ca. 4.5k cal a BP. This Late Holocene trend in sea ice change in the Chukchi and East Siberian Seas seems to be contemporaneous with similar changes in sea ice extent recorded from other Arctic marginal seas. The main factors controlling the millennial variability in sea ice (and surface‐water productivity) are probably changes in surface water and heat flow from the Pacific into the Arctic Ocean as well as the long‐term decrease in summer insolation. The short‐term centennial variability observed in the high‐resolution Middle Holocene record is probably related to solar forcing. Our new data on Holocene sea ice variability may contribute to synoptic reconstructions of regional to global Holocene climate change based on terrestrial and marine archives.

Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

“…This pattern suggests that millennial-scale variability in the BG was principally forced by changes in solar irradiance as the most likely forcing. Proxy records consistent with solar forcing were reported from a number of paleoclimatic archives, such as Chinese stalagmites (Hu et al, 2008), Yukon lake sediments (Anderson et al, 2005), and ice cores (Fisher et al, 2008), as well as marine sediments in the northwestern Pacific (Sagawa et al, 2014) and the Chukchi Sea (Stein et al, 2017). Because solar forcing is energetically much smaller than changes in the summer insolation caused by orbital forcing, we suppose that solar activity did not directly affect the stability of ice cover in the Canada Basin.…”

“…Nevertheless, we believe that the top of 01-GC is close to the sediment surface based on the biomarker distribution. IP 25 and brassicasterols show a downward decreasing trend in their concentrations in the top 10 cm (Stein et al, 2017). We suppose that this indicates their degradation with burial.…”

“…Age for core 01A-GC was constrained by seven accelerator mass spectrometry (AMS) 14 C ages of mollusc shells (Supplement Table S2; Stein et al, 2017). The core top in ARA 01-GC may not represent the modern age due to some sediment loss in the coring process.…”

“…Sea-ice concentrations in the Chukchi Sea during the Holocene were reconstructed by dinoflagellate cysts (de Vernal et al, 2005(de Vernal et al, , 2013Farmer et al, 2011) and biomarker IP 25 Stein et al, 2017).…”

“…8a; Stein et al, 2017), suggesting less sea-ice conditions in the periods. The low sea-ice concentration during 9-7.5 ka is consistent with the results of previous studies based on dinoflagellate cyst and IP 25 records showing the widespread sea-ice retreat in the Arctic Ocean, which was attributed to higher summer insolation during the early Holocene (Dyke and Savelle, 2001;Vare et al, 2009;de Vernal et al, 2013;Stein et al, 2017). On the other hand, the sea-ice retreat during 5.5-4 ka cannot be explained by higher summer insolation.…”