Bölling alleröd warming
Coastal permafrost was massively eroded during the Bølling-Allerød warm period
Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. The Bølling-Allerød interstadial 14,—12, years before present , during the last deglaciation, was characterized by rapid warming and sea level rise.
Yet, the response of the Arctic terrestrial cryosphere during this abrupt climate change remains thus far elusive.
Transient Simulation of Last Deglaciation with a New
Here we present a multi-proxy analysis of a sediment record from the northern Svalbard continental margin, an area strongly influenced by sea ice export from the Arctic, to elucidate sea level - permafrost erosion connections. We show that permafrost-derived material rich in biospheric carbon became the dominant source of sediments at the onset of the Bølling-Allerød, despite the lack of direct connections with permafrost deposits.
Our results suggest that the abrupt temperature and sea level rise triggered massive erosion of coastal ice-rich Yedoma permafrost, possibly from Siberian and Alaskan coasts, followed by long-range sea ice transport towards the Fram Strait and the Arctic Ocean gateway. Overall, we show how coastal permafrost is susceptible to large-scale remobilization in a scenario of rapid climate variability.
Abrupt pre-Bølling–Allerød warming and circulation changes in the deep ocean
The last deglaciation ca. The general reorganization of global climate during this period affected atmospheric and oceanic temperature, sea level and biogeochemical cycles 1 , 2 , particularly in the polar regions 3. This transition is characterised by a series of abrupt climate changes, including the Bølling-Allerød interstadial B-A; ca. The B-A period is also characterised by a rapid warming of the North Atlantic region 7 , 8 , and there is now a consensus that this climate transition was triggered by significant strengthening of the Atlantic Meridional Overturning Circulation AMOC 8 , 9 , During the B-A, the northern hemisphere climate experienced important modifications that share similarities with the anticipated Polar Amplification 12 , 13 , Thus, the study of past abrupt warming events offers the opportunity to understand the behaviour of permafrost in a scenario of rapid cryosphere retreat, as well as place the modern anthropogenically-induced permafrost-climate feedbacks into a broader context of natural centennial-scale climate variability.
Recent estimates indicate that the vast majority of carbon in permafrost regions during the LGM was found in loess and ice-rich deposits, while in modern times, considering the same areal extent, peatlands have become the dominant reservoir for organic carbon OC Overall, this indicates that a complete reorganization of OC reservoirs in Circumpolar Arctic soils must have taken place at some point during the last 20 kyr.
Today, the Yedoma domain represents approximately one third of the total OC stored in the Circumpolar Arctic permafrost region — Pg C , with Yedoma deposits accounting for Pg C 17 , In fact, previous modelling studies and records from coral reefs 25 , 26 also highlighted the potential contribution of Yedoma destabilization to deglacial atmospheric CO 2 increase.
Abrupt climate changes in the last two deglaciations - Nature
In contrast, a recent study has suggested that Yedoma deposits remained relatively unaltered during the last deglaciation, with negligible changes to their extension and storage capabilities However, during post-glacial sea level rise, when the continental shelves were flooded, Yedoma deposits possibly became vulnerable to mechanical erosion and thermal degradation 24 , 27 , In any case, a survey of the recent literature clearly reveals how the exact processes and feedbacks regarding Yedoma permafrost erosion during the last deglaciation are still a matter of debate, mainly because of the lack of past observational evidence and continuous records In this study, we present a multi-proxy analysis of a sediment gravity core HHGC collected in the upper slope north of Nortaustlandet continental margin, Svalbard Fig.
This area is characterized by an exceptionally high sedimentation rate during the last deglaciation 30 , 32 , 33 , which allows high-resolution paleoenvironmental reconstructions in a region where expanded, continuous records of the last Termination are rare. We combined a suite of terrestrial, marine and sea ice biomarkers lignin phenols, cutin acids, n -alkanes, alkenones, highly branched isoprenoids and sterols at high resolution, together with Compound Specific Radiocarbon Analyses CSRAs performed on individual high-molecular weight HMW n -alkanoic fatty acid methyl esters FAMEs , to characterise the land-ocean connections during the last 30 kyr in response to natural climate change.
Despite the lack of any direct riverine input proximal to the study area, we found an exceptionally high terrestrial biospheric contribution, starting when sea level rise was getting close to its maximum rate during the deglaciation MWP-1A; Fig. The extent of the major ice sheets of the northern hemisphere at ca. The grey area indicates the approximate extent of the exposed shelves at the onset of the B-A without accounting for glacial isostatic adjustment.
Green areas represent the current Yedoma deposit distribution 24 , also showing its remnants on the shelf.
Brown arrows indicate the main directions of sea ice transport out from the continental shelves and their merging towards the TPD. Main data plotted against calibrated age. The vertical dashed line displays the onset of MWP-1A. We used the gateway to the Arctic Ocean as a strategic region due to its relevance for sea ice export via the TPD Fig. Our final objective was to elucidate permafrost carbon reactivation mechanisms driven by abrupt climate warming and rapid sea level rise during MWP-1A.
We also compared our dataset with other previously obtained records from the Eurasian Arctic, most notably from cores PS 33 and PC 22 Fig. We developed a Bayesian age-depth model Supplementary Fig. The radiocarbon dates include 13 foraminiferal tests and one bivalve shell Supplementary Table 1 , of which 5 have been analysed in the current study and 9 published previously by Chauhan et al.