Regional seesaw between the North Atlantic and Nordic Seas during the last glacial abrupt climate events

Wary, Mélanie; Eynaud, Frédérique; Swingedouw, Didier; Masson‐Delmotte, Valérie; Matthießen, Jens; Kissel, Catherine; Zumaque, Jéna; Rossignol, Louise; Jouzel, Jean

doi:10.5194/cp-13-729-2017

Cited by 12 publications

(2 citation statements)

References 72 publications

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“…They have equally denoted a similar atypical pattern over the whole Nordic Seas during the LGM (de Vernal et al, 2005), pointing out here again discrepancies between different proxies of sea-surface conditions (de Vernal et al, 2006) that were also reported in other multiproxy studies (e.g., Penaud et al, 2011;. In most cases, these discrepancies have been suggested to likely result from differences in ecological strategies between producers (e.g., de Vernal et al, 2006;Wary et al, 2015Wary et al, , 2017a. Dinoflagellates, as well as coccolithophorids or diatoms, are mostly restricted to the uppermost 50 meters of the water column (e.g.…”

Section: Past Sea Ice Cover In the Northern Hemispheresupporting

confidence: 73%

Dinoflagellate fossils: Geological and biological applications

Penaud

Hardy

Lambert

et al. 2018

Revue de Micropaléontologie

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Dinoflagellates are part of the marine plankton and about 200 species produce a cyst (dinocyst) during their life cycle, these organic-walled sexually-produced cysts being fossilizable in sediments for hundreds of millions of years. Over the past 40-50 years, dinocysts have led to major advances on Mesozoic-Cenozoic research, in terms of biostratigraphy and paleogeogeography. Dinocyst taxonomy has then been continuously revised, with the tabulation being the main morphological link between living dinoflagellates and fossilized cysts. Over the Quaternary, and based on the principle of uniformitarianism (i.e. species ecology did not change through time), relationships between modern assemblages and present-day environmental factors controlling their distribution also allow for dinocystbased quantitative reconstructions derived from transfer function calculations. This paper presents a non-exhaustive review of the dinocyst literature allowing the reader to get a perspective about how they were discovered and defined, but also how they are applied in (paleo)ecological studies according to the timescale considered allowing then to provide useful insights into the future climate change and its associated ecological repercussions.

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Section: Past Sea Ice Cover In the Northern Hemispheresupporting

confidence: 73%

Dinoflagellate fossils: Geological and biological applications

Penaud

Hardy

Lambert

et al. 2018

Revue de Micropaléontologie

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“…2). Moreover, these age models have been validated by climate-independent tie points, such as tephra layers in core MD99-2284 43 , MD95-2010 44 and ENAM93-21 45 , or changes in the Earth’s magnetic field intensity in core MD99-2281 44 .…”

Section: Technical Validationmentioning

confidence: 99%

Consistently dated Atlantic sediment cores over the last 40 thousand years

et al. 2019

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Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.

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Circulation adjustment in the Arctic and Atlantic in response to Greenland and Antarctic mass loss

2021

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Following a high-end projection for mass loss from the Greenland and Antarctic ice-sheets, a freshwater forcing was applied to the ocean surface in the coupled climate model EC-Earthv2.2 to study the response to meltwater release assuming an RCP8.5 emission scenario. The meltwater forcing results in an overall freshening of the Atlantic that is dominated by advective changes, strongly enhancing the freshening due to dilution by Greenland meltwater release. The strongest circulation change occurs in the western North Atlantic subpolar gyre and in the gyre in the Nordic Seas, leaving the North Atlantic subpolar gyre the region where most advective salt export occurs. Associated with counteracting changes in both gyre systems, the response of the Atlantic Meridional Overturning Circulation is rather weak over the 190 years of the experiment; it reduces with only 1 Sv ($$= 10^6$$ = 10 6 m $$^3$$ 3 s $$^{-1}$$ - 1 ), compared to changes in the subpolar gyre of 5 Sv. This relative insensitivity of the AMOC to the forcing is attributed to enhanced convection in the Nordic Seas and stronger overflows that compensate reduced convection in the Labrador and Irminger Seas, and lead to higher sea surface temperatures (SSTs) in the former and lower SSTs in the latter region. The weakened subpolar gyre in the west also shifts the North Atlantic Current and the subpolar-subtropical gyre boundary; with the subtropical gyre expanding, and the western subpolar gyre contracting. The SST changes are associated with obduction of Atlantic waters in the Nordic Seas that would otherwise obduct in the western subpolar gyre. The anomalous SSTs also induce a coupled ocean-atmosphere feedback that further strengthens the Nordic Seas circulation and weakens the western subpolar gyre. This occurs because the anomalous SST-gradient enhances the westerlies, especially between 65$$^{\circ }$$ ∘ N and 70$$^{\circ }$$ ∘ N; the associated increase in windstress curl consequently enhances the gyre in the Nordic Seas. This feedback is driven by the Greenland mass loss; Antarctic meltwater discharge causes a weaker, opposite response and more particularly affects the South Atlantic salinity budget through northward advection of low-salinity waters from the Southern Ocean. This effect, however, becomes visible only hundred years after the onset of Antarctic mass loss. We conclude that the response to freshwater forcing from both ice caps can lead to a complex response in the Atlantic circulation systems with opposing effects in different subbasins. The relative strength of the response is time-dependent and largely governed by internal feedbacks; the forcing acts mainly as a trigger and is decoupled from the response.

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Regional seesaw between the North Atlantic and Nordic Seas during the last glacial abrupt climate events

Cited by 12 publications

References 72 publications

Dinoflagellate fossils: Geological and biological applications

Dinoflagellate fossils: Geological and biological applications

Consistently dated Atlantic sediment cores over the last 40 thousand years

Circulation adjustment in the Arctic and Atlantic in response to Greenland and Antarctic mass loss

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