Large Changes in Sea Ice Triggered by Small Changes in Atlantic Water Temperature

Jensen, Mari F.; Nisancioglu, Kerim H.; Spall, Michael A.

doi:10.1175/jcli-d-17-0802.1

Cited by 10 publications

(7 citation statements)

References 63 publications

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“…far south as the Greenland-Scotland Ridge at ∼60°N insulated the high-latitude atmosphere from the deep oceanic heat reservoir (23,24). Model simulations support a subsurface warming scenario under extended sea ice during GS (22,25,26) and suggest that a rapid removal of the sea ice cover might have caused the abrupt and high-amplitude D-O climate warming (11,12,14,15).…”

Section: Significancementioning

confidence: 94%

“…vigorous subpolar gyre circulation and enhanced ocean heat transport to the Norwegian Sea, leading to sea ice reduction (60). It has also been suggested that thermohaline convective instability beneath the stadial sea ice cover, resulting from subsurface warming and surface salinity changes, might have led to an abrupt sea ice decline and Greenland warming (15,25,26). It appears that, rather than a sole trigger, coupled atmosphere-sea ice-ocean dynamics in the subpolar North Atlantic, acting in a feedback loop under glacial boundary conditions, may have produced the D-O climate variability (60).…”

Section: Methodsmentioning

confidence: 99%

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Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes

Sadatzki

Maffezzoli

Dokken

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Constraining the past sea ice variability in the Nordic Seas is critical for a comprehensive understanding of the abrupt Dansgaard-Oeschger (D-O) climate changes during the last glacial. Here we present unprecedentedly detailed sea ice proxy evidence from two Norwegian Sea sediment cores and an East Greenland ice core to resolve and constrain sea ice variations during four D-O events between 32 and 41 ka. Our independent sea ice records consistently reveal a millennial-scale variability and threshold response between an extensive seasonal sea ice cover in the Nordic Seas during cold stadials and reduced seasonal sea ice conditions during warmer interstadials. They document substantial and rapid sea ice reductions that may have happened within 250 y or less, concomitant with reinvigoration of deep convection in the Nordic Seas and the abrupt warming transitions in Greenland. Our empirical evidence thus underpins the cardinal role of rapid sea ice decline and related feedbacks to trigger abrupt and large-amplitude climate change of the glacial D-O events.

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Section: Significancementioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes

Sadatzki

Maffezzoli

Dokken

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…Although a complete explanation for D-O variability remains elusive, a tentative scheme can be advanced. As there is strong coupling between sea-ice formation, deep-ocean convection in the Nordic Seas and the AMOC, a small perturbation in the heat or salt flux in the Nordic Seas, such as increased meltwater runoff from circum-Atlantic ice-sheets, a decrease in CO 2 or other climatic instabilities could lead to sea-ice advance 220 , a southward shift of the convection site 221 and AMOC weakening, thus leading to a stadial (Fig. 5b).…”

Section: [H1] Synthesis and Proposed Oscillatory Systemmentioning

confidence: 99%

An ice–climate oscillatory framework for Dansgaard–Oeschger cycles

Menviel

Skinner

Tarasov

et al. 2020

Nat Rev Earth Environ

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Intermediate glacial states were characterized by large temperature changes in Greenland and the North Atlantic, referred to as Dansgaard-Oeschger (D-O) variability, with some transitions occurring over a few decades. D-O variability included changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC), temperature changes of opposite sign and asynchronous timing in each hemisphere, shifts in the mean position of the Intertropical Convergence Zone and variations in atmospheric CO 2 . Palaeorecords and numerical studies indicate that the AMOC, with a tight coupling to Nordic Seas sea ice, is central to D-O variability, yet a complete theory remains elusive. In this Review, we synthesize the climatic expression and processes proposed to explain D-O cyclicity. What emerges is an oscillatory framework of the AMOC-sea-ice system, arising through feedbacks involving the atmosphere, cryosphere and the Earth's biogeochemical system. Palaeoclimate observations indicate that the AMOC might be more sensitive to perturbations than climate models currently suggest. Tighter constraints on AMOC stability are thus needed to project AMOC changes over the coming century as a response to anthropogenic carbon emissions. Progress can be achieved by additional observational constraints and numerical simulations performed with coupled climate-ice-sheet models. Key points• Abrupt warming events in Greenland and the North Atlantic, referred to as Dansgaard-Oeschger (D-O) events, were associated with changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC), global climate and the carbon cycle.• AMOC changes, with a tight coupling to Nordic Seas sea ice, strongly affect the climate and marine carbon cycle, and, in turn, ice-sheet mass balance. Resultant changes in oceanic wind stress, ocean heat content and salinity feed back on the AMOC.• Owing to the different timescales of the feedbacks, self-sustained AMOC oscillations could emerge during intermediate glacial states. The boundary conditions of intermediate glacial states (size of ice sheets, Bering Strait throughflow and concentration of atmospheric CO 2 appear to be key in enabling these oscillations.• Perturbations other than changes in meltwater input, including changes in atmospheric CO 2 or Northern Hemisphere ice-sheet height and extent, can lead to, and may be required for, D-O variability.• The relatively large and frequent AMOC changes associated with D-O variability suggest a relatively low AMOC stability during intermediate glacial states. This low stability is not evident in all numerical experiments performed with 1 coupled climate models, implying that some might either overestimate the AMOC stability or have a mismatch in the required background state for the low AMOC stability regime.• Additional observations on the location and strength of North Atlantic Deep Water formation and its link with sea ice, as well as its improved representation in climate models, are needed to better constrain future climate projections.Palaeopr...

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“…Regardless of the specific processes and feedbacks giving rise to persisting interglacial circulation anomalies, their existence indicates that non-linear behaviour in the climate-ocean system is not strictly confined to glacial intervals. To explain glacial millennial-scale variability Menviel et al (2020) proposed a self-sustained mode of the coupled climate-ice sheet system, whereby centennial-scale changes in freshwater balance (increased meltwater run-off from circum-Atlantic ice sheets); decreases in CO2 concentration; and/or changes in North Atlantic wind stress could lead to AMOC weakening, associated sea-ice advance (Jensen et al, 2018), and a southward shift of deep-water formation sites (Lynch-Stieglitz et al, 2006). Models are increasingly able to generate such bifurcations in ocean-atmosphere circulation, and thus climate, and an increasing number of models produce these transitions spontaneously (Brown and Galbraith, 2016;Vettoretti and Peltier, 2015).…”

Section: Discussionmentioning

confidence: 99%

Reorganization of Atlantic waters at sub-polar latitudes linked to deep water overflow in both glacial and interglacial climate states

Holmes

Babila

Ninnemann

et al. 2021

Preprint

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Abstract. Abrupt climate events are generally attributed as a characteristic of glacial (intermediate-to-large cryosphere) climate states. While a large cryosphere may be a necessary boundary condition for millennial-scale events to persist, it remains unclear whether high-magnitude climate variability is purely a glacial phenomenon requiring cryosphere-driven feedbacks. High-resolution climate records are used to portray North Atlantic climate's progression through low-ice, interglacial boundary conditions of Marine Isotope Stage (MIS) 11c into the glacial inception. We show that this period is marked by rapid shifts in both deep overflow and surface climate. The reorganization between polar and Atlantic waters at subpolar latitudes appears to accompany changes in the flow of deep water emanating from the Nordic Seas, regardless of magnitude or boundary conditions. Further, during both glacial and interglacial boundary conditions, we find that a reduction in deep water precedes surface hydrographic change. The existence of surface and deep ocean events during an interglacial, with similar magnitudes, abruptness, and surface-deep phasing as their glacial counterparts, alters our concept of “warm” climate stability and the requisite cryospheric thresholds and feedbacks for it.

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Large Changes in Sea Ice Triggered by Small Changes in Atlantic Water Temperature

Cited by 10 publications

References 63 publications

Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes

Rapid reductions and millennial-scale variability in Nordic Seas sea ice cover during abrupt glacial climate changes

An ice–climate oscillatory framework for Dansgaard–Oeschger cycles

Reorganization of Atlantic waters at sub-polar latitudes linked to deep water overflow in both glacial and interglacial climate states

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