Towards understanding potential atmospheric contributions to abrupt climate changes: Characterizing changes to the North Atlantic eddy-driven jet over the last deglaciation

Andres, Heather; Tarasov, Lev

doi:10.5194/cp-2018-153

Cited by 6 publications

(7 citation statements)

References 13 publications

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“…(2020) use preindustrial ice sheet. The differences in the ice sheet could affect the wind field over the North Atlantic and the location of the main deep‐water formation (Andres & Tarasov, 2019; Sherriff‐Tadano et al., 2018; Supporting Information Figure S12 in Kawamura et al., 2017; Figure 11 in Galbraith & de Lavergne, 2019). In our model with glacial ice sheets, surface winds over the North Atlantic are strong, and the main deep‐water formation is located near the center of the SPG because of the topography effect of the North American ice sheet (Sherriff‐Tadano et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Effect of Climatic Precession on Dansgaard‐Oeschger‐Like Oscillations

Kuniyoshi

Abe‐Ouchi

Sherriff‐Tadano

et al. 2022

Geophysical Research Letters

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Using the climate model MIROC4m, we simulate self‐sustained oscillations of millennial‐scale periodicity in the climate and Atlantic meridional overturning circulation under glacial conditions. We show two cases of extreme climatic precession and examine the mechanism of these oscillations. When the climatic precession corresponds to strong (weak) boreal seasonality, the period of the oscillation is about 1,500 (3,000) years. During the stadial, hot (cool) summer conditions in the Northern Hemisphere contribute to thin (thick) sea ice, which covers the deep convection sites, triggering early (late) abrupt climate change. During the interstadial, as sea ice is thin (thick), cold deep‐water forms and cools the subsurface quickly (slowly), which influences the stratification of the North Atlantic Ocean. We show that the oscillations are explained by the internal feedbacks of the atmosphere‐sea ice‐ocean system, especially subsurface ocean temperature change and salt advection feedback with a positive feedback between the subpolar gyre and deep convection.

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Section: Discussionmentioning

confidence: 99%

Effect of Climatic Precession on Dansgaard‐Oeschger‐Like Oscillations

Kuniyoshi

Abe‐Ouchi

Sherriff‐Tadano

et al. 2022

Geophysical Research Letters

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“…Changes in the southern extent or height of the LIS could also directly affect North Atlantic sea-ice concentration, temperature [195][196][197] and the AMOC 59 by modulating the strength and position of the North Atlantic westerlies. There is some evidence for a dynamic LIS during MIS 3: radiocarbon dates and relative sea-level constraints are consistent with a LIS southern margin proximal to the southern edge of Hudson Bay (∼51 • N) during the interstadial at 46.7 ka, followed by a fast southward advance to ∼44 • N during Heinrich stadial 4 and subsequent retreat 198 .…”

Section: [H1] Processes Involved In D-o Variabilitymentioning

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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“…The Younger Dryas surface forcing fields we use are monthly values derived from a coupled climate model configured for LGM using ICE-5G boundary conditions. This ice sheet configuration has been shown to generate more zonal atmospheric circulation patterns than more recent reconstructions of LGM ice sheets (Ullman et al, 2014), and LGM winds are expected to be stronger and more southward-shifted over the North Atlantic than winds during the Younger Dryas (Andres and Tarasov, 2019;Löfverström and Lora, 2017). These biases are expected to enhance zonal transport in the North Atlantic.…”

Section: Experimental Designmentioning

confidence: 85%

Eddy permitting simulations of freshwater injection from major Northern Hemisphere outlets during the last deglacial

Love

Andres

Condron

et al. 2021

Preprint

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Abstract. Freshwater, in the form of glacial runoff, is hypothesized to play a critical role in centennial to millennial scale climate variability such as the Younger Dryas and Dansgaard-Oeschger Events. Indeed, freshwater injection/hosing experiments with climate models have long shown that freshwater has the capability of generating such abrupt climate transitions. However, the relationship between freshwater and abrupt climate transitions is not straightforward. Large-scale glacial runoff events, such as Meltwater Pulse 1A, are not always temporally proximal to subsequent large-scale cooling. As well, the typical design of hosing experiments tends to artificially amplify the climate response. This study explores the impact that limitations in the representation of runoff in conventional hosing simulations has on our understanding of this relationship and addresses the more fundamental question of where coastally released freshwater is transported when it reaches the ocean. We focus particularly on the prior use of excessive freshwater volumes (often by a factor of 5) and present-day (rather than paleo) ocean gateways, as well as the injection of freshwater directly over sites of deep-water formation (DWF) rather than at runoff locations. We track the routing of glaciologically-constrained freshwater volumes from four different plausible injection locations in a suite of eddy-permitting glacial ocean simulations using MITGCM under both open and closed Bering Strait conditions. Restricting freshwater forcing values to realistic ranges results in less spreading of freshwater across the North Atlantic and indicates that the response of DWF depends strongly on the geographical location of meltwater input. In particular, freshwater released into the Gulf of Mexico has little impact on DWF regions as a result of turbulent mixing by the Gulf Stream. In contrast, freshwater released from the Eurasian Ice sheet or initially into the Arctic is found to have the largest impact on DWF in the North Atlantic and GIN seas. Additional experiments show that when the Bering Strait is open, much like present-day, the Mackenzie River source exhibits twice as much freshening of the Labrador sea as a closed Bering Strait. Finally, our results illustrate that applying a freshwater hosing directly into the North Atlantic with even realistic freshwater amounts still over-estimates the effect of terrestrial runoff on ocean circulation.

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Towards understanding potential atmospheric contributions to abrupt climate changes: Characterizing changes to the North Atlantic eddy-driven jet over the last deglaciation

Cited by 6 publications

References 13 publications

Effect of Climatic Precession on Dansgaard‐Oeschger‐Like Oscillations

Effect of Climatic Precession on Dansgaard‐Oeschger‐Like Oscillations

An ice–climate oscillatory framework for Dansgaard–Oeschger cycles

Eddy permitting simulations of freshwater injection from major Northern Hemisphere outlets during the last deglacial

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