The revised Quaternary climatostratigraphy of the Arctic Ocean: linkages with insolation and sea-level changes

The revised late Pleistocene chronostratigraphy of the Arctic Ocean based on the pre-2000 magnetostratigraphic interpretation and chronological information from the decay of U-series daughter isotopes in sediments leads to reassigning "warm" vs "cold" climatostratigraphic intervals to distinct interglacial, interstadial, or stadial stages and shows a realistic linkage with high latitude insolation parameters and the global sea-level history. "Warm" episodes then match intervals with summer season insolation and sea-level elevation peaking above those of the early Holocene. Whereas the whole summer season insolation governs heat fluxes towards the Arctic Ocean, in relation with the North Atlantic Water inflow, sea level plays a complementary role as it governs the submergence of the Arctic Ocean shelves and the development of “sea-ice factories”. Sea level also controls the flux of warm and low-salinity Pacific water through the shallow Bering Strait, thus the heat budget of the Western Arctic and the salinity budget of the whole Arctic Ocean. The combination of both parameters indicates that climate conditions during recent interglacials were of distinct amplitude and timing vs those at lower latitudes. From MIS 10 to MIS 1, five short "warm" intervals (MIS 1, 3, 5e, 7, 9) were characterized by sea-ice rafting deposition of smectite and detrital carbonate-rich sediments with ²³⁰Th-excesses along major drifting sea-ice routes TransPolar Drift; Beaufort Gyre). These layers alternate with coarser layers linked to sporadic and short-duration, Circum-Arctic glacier surges, deposited during stadials. In contradistinction, the MIS 14 to MIS 10 interval have experienced a thick ice-cover (perennial ice or ice shelf) during long periods, including MIS 11 and possibly MIS 13. These interglacials depict relatively a low summer season insolation in contrast with that of other interglacials. Another feature merging from this revision is the shortness of the intervals with seasonally open sea-ice conditions. Often recorded by a few cm-thick sedimentary layers, these intervals are in phase with the mean summer season insolation (not the June solstice peak) and may have lasted a few ka at most, based on the example of the Holocene. Feedbacks from the Arctic Ocean towards climate/ocean conditions at lower latitudes include i) the effect of its sea-ice on albedo and latitudinal pressure gradients, and ii) the impact of its freshwater export on the Atlantic Meridional Overturning Circulation (AMOC). Due to its specific response to insolation and sea-level changes, the Arctic Ocean may have thus triggered out of phase climate and AMOC fluctuations during interglacials at lower latitudes, but it has globally remained a sediment-starved glacial ocean throughout most of the Brunhes epoch.