The emergence of modern sea ice cover in the Arctic Ocean

Knies, Jochen; Cabedo‐Sanz, Patricia; Belt, Simon T.; Baranwal, Soma; Fietz, Susanne; Rosell‐Melé, Antoni

doi:10.1038/ncomms6608

Cited by 120 publications

(145 citation statements)

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“…Many hypotheses have been put forward to explain the initiation of these NH glaciations around the Pliocene-Pleistocene transition interval. Causes include tectonics (Keigwin, 1982;Raymo, 1994;Haug and Tiedemann, 1998;Knies et al, 2014;Poore et al, 2006), orbital forcing dominated by obliquity-paced variability (Hays et al, 1976;Maslin et al, 1998;Raymo et al, 2006), and atmospheric CO 2 concentration decline (Pagani et al, 2010;Seki et al, 2010;Bartoli et al, 2011) driven by, for example, changes in ocean stratification that affected the biological pump (Haug et al, 1999). Changes were amplified by NH albedo changes (Lawrence et al, 2010), evaporation feedbacks (Haug et al, 2005), and possibly tropical atmospheric circulation change and breakdown of a permanent El Niño (Ravelo et al, 2004;Brierley and Fedorov, 2010;Etourneau et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Land–sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing

et al. 2018

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Abstract. We assess the disputed phase relations between forcing and climatic response in the early Pleistocene with a spliced Gelasian ( ∼ 2.6-1.8 Ma) multi-proxy record from the southern North Sea basin. The cored sections couple climate evolution on both land and sea during the intensification of Northern Hemisphere glaciation (NHG) in NW Europe, providing the first well-constrained stratigraphic sequence of the classic terrestrial Praetiglian stage. Terrestrial signals were derived from the Eridanos paleoriver, a major fluvial system that contributed a large amount of freshwater to the northeast Atlantic. Due to its latitudinal position, the Eridanos catchment was likely affected by early Pleistocene NHG, leading to intermittent shutdown and reactivation of river flow and sediment transport. Here we apply organic geochemistry, palynology, carbonate isotope geochemistry, and seismostratigraphy to document both vegetation changes in the Eridanos catchment and regional surface water conditions and relate them to early Pleistocene glacial-interglacial cycles and relative sea level changes. Paleomagnetic and palynological data provide a solid integrated timeframe that ties the obliquity cycles, expressed in the borehole geophysical logs, to Marine Isotope Stages (MIS) 103 to 92, independently confirmed by a local benthic oxygen isotope record. Marine and terrestrial palynological and organic geochemical records provide high-resolution reconstructions of relative terrestrial and sea surface temperature (TT and SST), vegetation, relative sea level, and coastal influence.During the prominent cold stages MIS 98 and 96, as well as 94, the record indicates increased non-arboreal vegetation, low SST and TT, and low relative sea level. During the warm stages MIS 99, 97, and 95 we infer increased stratification of the water column together with a higher percentage of arboreal vegetation, high SST, and relative sea level maxima. The early Pleistocene distinct warm-cold alterations are synchronous between land and sea, but lead the relative sea level change by 3000-8000 years. The record provides evPublished by Copernicus Publications on behalf of the European Geosciences Union. 398T. H. Donders et al.: Land-sea coupling of early Pleistocene glacial cycles idence for a dominantly Northern Hemisphere-driven cooling that leads the glacial buildup and varies on the obliquity timescale. Southward migration of Arctic surface water masses during glacials, indicated by cool-water dinoflagellate cyst assemblages, is furthermore relevant for the discussion on the relation between the intensity of the Atlantic meridional overturning circulation and ice sheet growth.

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Section: Introductionmentioning

confidence: 99%

Land–sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing

et al. 2018

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“…Unprecedented changes over the last 40 years consign the Arctic to a climate trajectory unobserved in more than two million years with an ice-free summertime Arctic expected by mid-century [28][29][30][31]. Other ongoing changes, such as mountain glacier mass loss, Greenland Ice Sheet melt, vegetation type, ecosystem structure, and permafrost thaw [32][33][34][35][36][37] also illustrate a shifting Arctic climate.…”

Section: Introductionmentioning

confidence: 99%

On the Increasing Importance of Air-Sea Exchanges in a Thawing Arctic: A Review

et al. 2018

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Forty years ago, climate scientists predicted the Arctic to be one of Earth's most sensitive climate regions and thus extremely vulnerable to increased CO 2 . The rapid and unprecedented changes observed in the Arctic confirm this prediction. Especially significant, observed sea ice loss is altering the exchange of mass, energy, and momentum between the Arctic Ocean and atmosphere.As an important component of air-sea exchange, surface turbulent fluxes are controlled by vertical gradients of temperature and humidity between the surface and atmosphere, wind speed, and surface roughness, indicating that they respond to other forcing mechanisms such as atmospheric advection, ocean mixing, and radiative flux changes. The exchange of energy between the atmosphere and surface via surface turbulent fluxes in turn feeds back on the Arctic surface energy budget, sea ice, clouds, boundary layer temperature and humidity, and atmospheric and oceanic circulations. Understanding and attributing variability and trends in surface turbulent fluxes is important because they influence the magnitude of Arctic climate change, sea ice cover variability, and the atmospheric circulation response to increased CO 2 . This paper reviews current knowledge of Arctic Ocean surface turbulent fluxes and their effects on climate. We conclude that Arctic Ocean surface turbulent fluxes are having an increasingly consequential influence on Arctic climate variability in response to strong regional trends in the air-surface temperature contrast related to the changing character of the Arctic sea ice cover. Arctic Ocean surface turbulent energy exchanges are not smooth and steady but rather irregular and episodic, and consideration of the episodic nature of surface turbulent fluxes is essential for improving Arctic climate projections.

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“…In addition to the sites used in Howell et al (2014), mid-Pliocene Arctic SST estimates from 146 Schreck et al (2013) and Knies et al (2014), are included. The SST estimate for ODP 911 from…”

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confidence: 99%

“…Understanding of the state of Arctic sea ice from proxy data in the mid-Pliocene remains lim- of IP 25 , a sea ice proxy biomarker (Belt et al, 2007;Brown et al, 2014), in two cores (located at Knies et al (2014) shows that the mid-Pliocene minimum sea 49 ice margin was located to the north of these two sites. Cronin et al (1993), Moran et al (2006) and 50 Polyak et al (2010) show evidence from ostracode assemblages and ice rafted debris that appear 51 to suggest that the mid-Pliocene Arctic sea ice cover was seasonal in nature.…”

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confidence: 99%

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Sensitivity of Pliocene Arctic climate to orbital forcing, atmospheric CO2 and sea ice albedo parameterisation

Howell

Haywood

Dowsett

et al. 2016

Earth and Planetary Science Letters

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Arctic conditions. Given the strong influence that sea ice exerts on high latitude temperatures, an 8 enhanced understanding of the nature of mPWP Arctic sea ice would be highly beneficial. 9Using the HadCM3 GCM, this paper explores the impact of various combinations of potential 10 mPWP orbital forcing, atmospheric CO 2 concentrations and minimum sea ice albedo on sea ice 11 extent and high latitude warming. The focus is on the Northern Hemisphere, due to availability 12 of proxy data, and the large data-model discrepancies in this region. Changes in orbital forcings 13 are demonstrated to be sufficient to alter the Arctic sea ice simulated by HadCM3 from perennial 14 to seasonal. However, this occurs only when atmospheric CO 2 concentrations exceed 300 ppm. 15Reduction of the minimum sea ice albedo from 0.5 to 0.2 is also sufficient to simulate seasonal sea

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The emergence of modern sea ice cover in the Arctic Ocean

Cited by 120 publications

References 66 publications

Land–sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing

Land–sea coupling of early Pleistocene glacial cycles in the southern North Sea exhibit dominant Northern Hemisphere forcing

On the Increasing Importance of Air-Sea Exchanges in a Thawing Arctic: A Review

Sensitivity of Pliocene Arctic climate to orbital forcing, atmospheric CO2 and sea ice albedo parameterisation

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