Deglacial floods in the Beaufort Sea preceded Younger Dryas cooling

Keigwin, Lloyd D; Klotsko, Shannon; Zhao, Ning; Reilly, Brendan; Giosan, Liviu; Driscoll, Neal W.

doi:10.1038/s41561-018-0169-6

Cited by 101 publications

(85 citation statements)

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“…Additionally, riverbank erosion of permafrost due to retreating American ice sheets (Keigwin et al 2018) and mountain glaciers on Kamchatka (Bigg et al 2008) may have proceeded throughout the late deglaciation.…”

Section: Sample Depth (Cm)mentioning

confidence: 99%

Permafrost-carbon mobilization in Beringia caused by deglacial meltwater runoff, sea-level rise and warming

Meyer

Hefter

Köhler

et al. 2019

Environ. Res. Lett.

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During the last deglaciation (18-8 kyr BP), shelf flooding and warming presumably led to a large-scale decomposition of permafrost soils in the mid-to-high latitudes of the Northern Hemisphere. Microbial degradation of old organic matter released from the decomposing permafrost potentially contributed to the deglacial rise in atmospheric CO 2 and also to the declining atmospheric radiocarbon contents (Δ 14 C). The significance of permafrost for the atmospheric carbon pool is not well understood as the timing of the carbon activation is poorly constrained by proxy data. Here, we trace the mobilization of organic matter from permafrost in the Pacific sector of Beringia over the last 22 kyr using mass-accumulation rates and radiocarbon signatures of terrigenous biomarkers in four sediment cores from the Bering Sea and the Northwest Pacific. We find that pronounced reworking and thus the vulnerability of old organic carbon to remineralization commenced during the early deglaciation (∼16.8 kyr BP) when meltwater runoff in the Yukon River intensified riverbank erosion of permafrost soils and fluvial discharge. Regional deglaciation in Alaska additionally mobilized significant fractions of fossil, petrogenic organic matter at this time. Permafrost decomposition across Beringia's Pacific sector occurred in two major pulses that match the Bølling-Allerød and Preboreal warm spells and rapidly initiated within centuries. The carbon mobilization likely resulted from massive shelf flooding during meltwater pulses 1A (∼14.6 kyr BP) and 1B (∼11.5 kyr BP) followed by permafrost thaw in the hinterland. Our findings emphasize that coastal erosion was a major control to rapidly mobilize permafrost carbon along Beringia's Pacific coast at ∼14.6 and ∼11.5 kyr BP implying that shelf flooding in Beringia may partly explain the centennial-scale rises in atmospheric CO 2 at these times. Around 16.5 kyr BP, the mobilization of old terrigenous organic matter caused by meltwater-floods may have additionally contributed to increasing CO 2 levels.

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Section: Sample Depth (Cm)mentioning

confidence: 99%

Permafrost-carbon mobilization in Beringia caused by deglacial meltwater runoff, sea-level rise and warming

Meyer

Hefter

Köhler

et al. 2019

Environ. Res. Lett.

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“…Still, it most likely resulted from a combination of processes (e.g. Kohfeld and Ridgwell, 2009), including changes in solubility, global alkalinity content (e.g. Sigman et al, 2010), iron fertilization (e.g.…”

Section: Introductionmentioning

confidence: 99%

The penultimate deglaciation: protocol for Paleoclimate Modelling Intercomparison Project (PMIP) phase 4 transient numerical simulations between 140 and 127 ka, version 1.0

et al. 2019

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Abstract. The penultimate deglaciation (PDG, ∼138–128 thousand years before present, hereafter ka) is the transition from the penultimate glacial maximum (PGM) to the Last Interglacial (LIG, ∼129–116 ka). The LIG stands out as one of the warmest interglacials of the last 800 000 years (hereafter kyr), with high-latitude temperature warmer than today and global sea level likely higher by at least 6 m. Considering the transient nature of the Earth system, the LIG climate and ice-sheet evolution were certainly influenced by the changes occurring during the penultimate deglaciation. It is thus important to investigate, with coupled atmosphere–ocean general circulation models (AOGCMs), the climate and environmental response to the large changes in boundary conditions (i.e. orbital configuration, atmospheric greenhouse gas concentrations, ice-sheet geometry and associated meltwater fluxes) occurring during the penultimate deglaciation. A deglaciation working group has recently been set up as part of the Paleoclimate Modelling Intercomparison Project (PMIP) phase 4, with a protocol to perform transient simulations of the last deglaciation (19–11 ka; although the protocol covers 26–0 ka). Similar to the last deglaciation, the disintegration of continental ice sheets during the penultimate deglaciation led to significant changes in the oceanic circulation during Heinrich Stadial 11 (∼136–129 ka). However, the two deglaciations bear significant differences in magnitude and temporal evolution of climate and environmental changes. Here, as part of the Past Global Changes (PAGES)-PMIP working group on Quaternary interglacials (QUIGS), we propose a protocol to perform transient simulations of the penultimate deglaciation under the auspices of PMIP4. This design includes time-varying changes in orbital forcing, greenhouse gas concentrations, continental ice sheets as well as freshwater input from the disintegration of continental ice sheets. This experiment is designed for AOGCMs to assess the coupled response of the climate system to all forcings. Additional sensitivity experiments are proposed to evaluate the response to each forcing. Finally, a selection of paleo-records representing different parts of the climate system is presented, providing an appropriate benchmark for upcoming model–data comparisons across the penultimate deglaciation.

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“…The diversion of drainage is consistent with a δ 18 O anomaly measured in sediment cores from the Gulf of Mexico, which was caused by a sudden lack of freshwater input at the beginning of the YD (~12.9 ka bp ) (Wickert et al ., ). However, there is still debate as to whether this rerouting of Lake Agassiz overflow happened towards the east (Carlson et al ., ; Wickert et al ., ; Leydet et al ., ) or towards the Arctic via the Mackenzie River (Murton et al ., ; Keigwin et al ., ). These different drainage routes are marked as green arrows in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The ice margin blocking the northwestern drainage route does not necessarily contradict the freshening of the Beaufort Sea at the beginning of the YD, as reported by Keigwin et al . (). The source of this signal can be attributed to the rapid deglaciation of the northwestern LIS (Tarasov and Peltier, ) and drainage events of other major proglacial lakes in this region, such as Lake McConnell or Lake Peace (Wickert, ).…”

Section: Discussionmentioning

confidence: 99%

LakeCC: a tool for efficiently identifying lake basins with application to palaeogeographic reconstructions of North America

Hinck

Gowan

Lohmann

2019

J Quaternary Science

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Along the margins of continental ice sheets, lakes formed in isostatically depressed basins during glacial retreat. Their shorelines and extent are sensitive to the ice margin and the glacial history of the region. Proglacial lakes, in turn, also impact the glacial isostatic adjustment due to loading, and ice dynamics by posing a marine‐like boundary condition at the ice margin. In this study we present a tool that efficiently identifies lake basins and the corresponding maximum water level for a given ice sheet and topography reconstruction. This algorithm, called the LakeCC model, iteratively checks the whole map for a set of increasing water levels and fills isolated basins until they overflow into the ocean. We apply it to the present‐day Great Lakes and the results show good agreement (∼1−4%) with measured lake volume and depth. We then apply it to two topography reconstructions of North America between the Last Glacial Maximum and the present. The model successfully reconstructs glacial lakes such as Lake Agassiz, Lake McConnell and the predecessors of the Great Lakes. LakeCC can be used to judge the quality of ice sheet reconstructions. © 2019 The Authors Journal of Quaternary Science Published by John Wiley & Sons Ltd.

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Deglacial floods in the Beaufort Sea preceded Younger Dryas cooling

Cited by 101 publications

References 50 publications

Permafrost-carbon mobilization in Beringia caused by deglacial meltwater runoff, sea-level rise and warming

Permafrost-carbon mobilization in Beringia caused by deglacial meltwater runoff, sea-level rise and warming

The penultimate deglaciation: protocol for Paleoclimate Modelling Intercomparison Project (PMIP) phase 4 transient numerical simulations between 140 and 127 ka, version 1.0

LakeCC: a tool for efficiently identifying lake basins with application to palaeogeographic reconstructions of North America

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