Natural variability of the Arctic Ocean sea ice during the present interglacial

Abstract

The impact of the ongoing anthropogenic warming on the Arctic Ocean sea ice is ascertained and closely monitored. However, its long-term fate remains an open question as its natural variability on centennial to millennial timescales is not well documented. Here, we use marine sedimentary records to reconstruct Arctic sea-ice fluctuations. Cores collected along the Lomonosov Ridge that extends across the Arctic Ocean from northern Greenland to the Laptev Sea were radiocarbon dated and analyzed for their micropaleontological and palynological contents, both bearing information on the past sea-ice cover. Results demonstrate that multiyear pack ice remained a robust feature of the western and central Lomonosov Ridge and that perennial sea ice remained present throughout the present interglacial, even during the climate optimum of the middle Holocene that globally peaked ∼6,500 y ago. In contradistinction, the southeastern Lomonosov Ridge area experienced seasonally sea-ice-free conditions, at least, sporadically, until about 4,000 y ago. They were marked by relatively high phytoplanktonic productivity and organic carbon fluxes at the seafloor resulting in low biogenic carbonate preservation. These results point to contrasted west–east surface ocean conditions in the Arctic Ocean, not unlike those of the Arctic dipole linked to the recent loss of Arctic sea ice. Hence, our data suggest that seasonally ice-free conditions in the southeastern Arctic Ocean with a dominant Arctic dipolar pattern, may be a recurrent feature under “warm world” climate.

Did agriculture beget agriculture during the past several millennia?

“…A direct comparison with 19th century proxy records or historical climate observations would not be compatible with the hypothesized late-Holocene climate evolutions represented by ORBITAL and NATURAL. Nevertheless, many of the changes illustrated in Figure 5 are consistent with known climate trends during the past millennia, such as the weakening of boreal summer monsoons, pronounced cooling in mid-high latitudes, and increasing Arctic sea ice cover (de Vernal et al, 2020; Marcott et al, 2013; Zhao and Harrison, 2012).…”

Vulnerability of the North Water ecosystem to climate change

“…The NAO/AO have shown periodicities on multidecadal timescales that are linked with sea-surface temperature changes in the North Atlantic (Atlantic Multidecadal Variability (AMV)), in turn influencing Arctic sea-ice variability 39,40 . Sea ice concentration and motion in the Arctic Ocean region are also highly impacted by the Dipole Anomaly (DA) pattern-the second mode of winter variability -which promotes sea ice transport from the western to the eastern Arctic Ocean and export towards the North Atlantic through Fram Strait, and appears to be particularly important during warmer periods [41][42][43] . From c. 4400 to 2700 cal yrs b2k, the polynya remained relatively stable and productive, and paleo-records point towards predominantly weakly positive NAO and low magnitude variations in the AO during this period (refs.…”

Challenging the hypothesis of an Arctic Ocean lake during recent glacial episodes

“…2017). Interglacials are not necessarily better recorded in the central Arctic Ocean, based on the example of the Holocene (De Vernal et al ., 2020). In an ocean where a large part of the sedimentary transport is linked to ice‐rafting (sea ice and/or icebergs; Clark and Hanson, 1983), such sedimentary gaps either indicate the presence of perennial sea ice or of an ice shelf, in the concerned basin areas.…”

“…These events are recorded by a few centimetres at most, deposited within a short time window, as illustrated by the layer assigned to the Holocene interglacial. This millennial‐scale sedimentary layer was deposited during the early/middle Holocene transition as suggested by calibrated 14 C ages peaking at ~8 ka bp (Hillaire‐Marcel et al ., 2017; De Vernal et al ., 2020). It was deposited during an interval marked by a rising sea level and high summer insolation (Hillaire‐Marcel et al ., 2022).…”

“…It was deposited during an interval marked by a rising sea level and high summer insolation (Hillaire‐Marcel et al ., 2022). Both factors led to the development of sea‐ice factories in the East Siberian Sea fostering intense productivity (De Vernal et al ., 2020), and the drifting of ice rafts releasing sediment previously uploaded over shelves, along the Transpolar Drift and the Beaufort Gyre routes (Fig. 1).…”