Keeping an Eye on Antarctic Ice Sheet Stability

Escutia, Carlota; DeConto, Robert M.; Dunbar, Robert B.; Santis, Laura De; Shevenell, A.; Naish, Timothy R.

doi:10.5670/oceanog.2019.117

Cited by 25 publications

(22 citation statements)

References 81 publications

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“…During 2018-2019 there were three IODP expeditions to the Southern Ocean, some of these campaigns have recovered material from the Miocene (McKay et al, 2018). In addition to ship-based drilling, sea ice-based platform drilling has recovered Miocene marine sediments from the Ross Sea -a recent overview of marine drilling campaigns around Antarctica is given in Escutia et al, (2019). A variety of methods are used to determine past change of the AIS.…”

Section: Ice-proximal Recordsmentioning

confidence: 99%

The Miocene: The Future of the Past

Steinthorsdottir

Coxall

Boer

et al. 2021

Paleoceanog and Paleoclimatol

271

179

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The Miocene epoch (23.03-5.33 Ma) was a time interval of global warmth, relative to today.Continental configurations and mountain topography transitioned toward modern conditions, and many flora and fauna evolved into the same taxa that exist today. Miocene climate was dynamic: long periods of early and late glaciation bracketed a ∼2 Myr greenhouse interval-the Miocene Climatic Optimum (MCO). Floras, faunas, ice sheets, precipitation, pCO 2 , and ocean and atmospheric circulation mostly (but not ubiquitously) covaried with these large changes in climate. With higher temperatures and moderately higher pCO 2 (∼400-600 ppm), the MCO has been suggested as a particularly appropriate analog for future climate scenarios, and for assessing the predictive accuracy of numerical climate models-the same models that are used to simulate future climate. Yet, Miocene conditions have proved difficult to reconcile with models. This implies either missing positive feedbacks in the models, a lack of knowledge of past climate forcings, or the need for re-interpretation of proxies, which might mitigate the model-data discrepancy. Our understanding of Miocene climatic, biogeochemical, and oceanic changes on broad spatial and temporal scales is still developing. New records documenting the physical, chemical, and biotic aspects of the Earth system are emerging, and together provide a more comprehensive understanding of this important time interval. Here, we review the state-of-the-art in Miocene climate, ocean circulation, biogeochemical cycling, ice sheet dynamics, and biotic adaptation research as inferred through proxy observations and modeling studies. Plain Language Summary During the Miocene time period (∼23-5 million years ago),Planet Earth looked similar to today, with some important differences: the climate was generally warmer and highly variable, while atmospheric CO 2 was not much higher. Continental-sized ice sheets were only present on Antarctica, but not in the northern hemisphere. The continents drifted to near their modernday positions, and plants and animals evolved into the many (near) modern species. Scientists study the Miocene because present-day and projected future CO 2 levels are in the same range as those reconstructed for the Miocene. Therefore, if we can understand climate changes and their biotic responses from the Miocene past, we are able to better predict current and future global changes. By comparing Miocene climate reconstructions from fossil and chemical data to climate simulations produced by computer models, scientists are able to test their understanding of the Earth system under higher CO 2 and warmer conditions than those of today. This helps in constraining future warming scenarios for the coming STEINTHORSDOTTIR ET AL.

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Section: Ice-proximal Recordsmentioning

confidence: 99%

The Miocene: The Future of the Past

Steinthorsdottir

Coxall

Boer

et al. 2021

Paleoceanog and Paleoclimatol

271

179

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“…While Antarctica slowly drifted southward and the Passage widened (Eagles & Jokat, ; Lawver & Gahagan, ; Livermore et al, ; Scher & Martin, ) and global atmospheric CO 2 dropped significantly (Beerling & Royer, ; Pagani et al, ; Y.G. Zhang et al, ), the Antarctic continent became oceanographically isolated, and its environment changed to a polar climate (Cristini et al, ; DeConto & Pollard, ; Escutia et al, ; Galeotti et al, ; Mackensen & Ehrmann, ; Pollard et al, ). Little is known about the exact size and dynamics of the Oligocene Antarctic Ice Sheet.…”

Section: Geological Evolution and Present‐day Deposition Patternsmentioning

confidence: 99%

“… Despite the progress achieved over the last two decades in reconstructing the timing and processes of gateway opening around Antarctica during the last ca. 45 Ma, questions relating to the development of the WG are still unresolved, because of the lack of scientific drill holes (Escutia et al, ). For example, it is unclear (a) how the WG's current system changed in response to the opening of the nearby Drake Passage gateway and thus numerical models simulating these changes (e.g., England et al, ; Yang et al, ) remain untested, and (b) whether the subsidence of the seafloor in Drake Passage and the neighboring Scotia Sea below a distinct paleo‐bathymetric threshold depth was required for the full development of the ACC and the WG. The role of the growing Antarctic ice sheets since the late Paleogene for steepening the atmospheric meridional temperature gradient and thus strengthening the Southern Hemisphere westerlies and initiating the clockwise flowing ACC and the WG is still unclear.…”

Section: Geological Evolution and Present‐day Deposition Patternsmentioning

confidence: 99%

The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges

Vernet

Geibert

Hoppema

et al. 2019

Reviews of Geophysics

154

147

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The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures, and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide, and global modeling efforts—thereby enhancing predictions of the WG in global ocean circulation and climate.

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“…Here, terrestrial history is inferred from pollen and spores, plant fragments, nonmarine diatoms and chrysophyte cysts, long-chain plant leaf waxes (Eglinton & Hamilton, 1967), high BIT index values and abundant branched GDGTs (Weijers et al, 2006;Weijers et al, 2007). Age control for these deposits comes from biostratigraphic assessment of marine diatoms and other microfossils, which has been established over the last >50 years of global ocean and Antarctic drilling (Barron et al, 2015;Escutia et al, 2019) (e.g., DSDP, ODP, IODP, CRP-3, and CIROS-1; Texts S1 and S5).…”

Section: Methodsmentioning

confidence: 99%

“…The only available direct geological evidence of WARS Paleogene basin strata is eroded and mixed subglacial sediments recovered by hot water drilling through Siple and Gould Coast ice streams. Sparse in situ Paleogene deposits are known from outcrop, drill cores and dredge samples from around Antarctica, rare Paleogene glacial erratic cobbles have been identified, and shipboard seismic studies have imaged inferred Paleogene deposits on the continental shelf such as Coulman High (e.g., De Santis et al, ; Escutia et al, ). Rare glacial sediments recovered from beneath the West Antarctic Ice Sheet (WAIS), far from any subaerially exposed landmasses, contain regionally or locally displaced and mixed microfossil and biomarker evidence of Paleogene deposition in the basin interior (Texts S1 and S2 in the supporting information).…”

Section: Introductionmentioning

confidence: 99%

Paleogene Marine and Terrestrial Development of the West Antarctic Rift System

Coenen

Scherer

Baudoin

et al. 2020

Geophysical Research Letters

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Modeling the early development of the West Antarctic Ice Sheet (WAIS) hinges on the configuration and evolution of Paleogene terrestrial landscapes associated with the West Antarctic Rift System. A widely applied but previously untested paleotopographic reconstruction for the Eocene/Oligocene boundary suggests that much of central West Antarctica was as much as 1,000 m above sea level at that time, constituting a key nucleating site for an early WAIS. Here we show that Paleogene age marine and terrestrial microfossil assemblages and biomarkers in sediments recovered from beneath the WAIS provide direct evidence contrary to this widely utilized “maximum” paleotopographic reconstruction. These new constraints call for significantly modified tectonic and ice sheet model parameterization and also provide insights into modern differential uplift across the West Antarctic Rift System.

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Keeping an Eye on Antarctic Ice Sheet Stability

Cited by 25 publications

References 81 publications

The Miocene: The Future of the Past

The Miocene: The Future of the Past

The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges

Paleogene Marine and Terrestrial Development of the West Antarctic Rift System

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