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21 results on '"Fogwill, C.J."'

1. Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years

Author

Weber, M.E., Bailey, I., Hemming, S.R., Martos, Y.M., Reilly, B.T., Ronge, T.A., Brachfeld, S., Williams, T., Raymo, M., Belt, M., Smik, L., vogel, H., Peck, V., Armbrecht, L., Cage, A., Cardillo, F.G., Du, Z., Fauth, G., Fogwill, C.J., and García-García, M. (Margarita)

Subjects
carbon, carbon cycle, pleistocene, Medio Marino, Centro Oceanográfico de Cádiz, ice ages, antarctic zone
Abstract

The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels., SI

Published
2022

2. The multi-millennial Antarctic commitment to future sea-level rise

Author

Golledge, N.R., Kowalewski, D.E., Naish, T.R., Levy, R.H., Fogwill, C.J., and Gasson, E.G.W.

Subjects
Surface-ice melting -- Environmental aspects, Global warming -- Environmental aspects, Sea level -- Environmental aspects, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Atmospheric warming is projected to increase global mean surface temperatures by 0.3 to 4.8 degrees Celsius above pre-industrial values by the end of this century (1). If anthropogenic emissions continue [...]

Published
2015

6. Cosmogenic nuclides [sup.10]Be and [sup.26]Al imply limited Antarctic Ice Sheet thickening and low erosion in the Shackleton Range for >1 m.y

Author

Fogwill, C.J., Bentley, M.J., Sugden, D.E., Kerr, A.R., and Kubik, P.W.

Subjects
Earth sciences
Abstract

Concentrations of the cosmogenic nuclides [sup.10]Be and [sup.26]Al on bedrock surfaces in the Shackleton Range, Antarctica, indicate minimum exposure ages between 3.0 [+ or -] 0.3 and 1.16 [+ or -] 0.10 Ma. The isotope data indicate that the maximum long-term erosion rate is 0.10-0.35 m/m.y., and the ratios suggest no prolonged periods of burial by cold-based ice. The findings are important because of the location of the massif close to the junction of the East Antarctic Ice Sheet and the landward extent of the Filchner Ice Shelf. These results point to three conclusions. First, the massif has not been overridden by the East Antarctic Ice Sheet during the late Quaternary. Rather, moraines 200-340 m above outlet glaciers are likely to represent the maximum thickening of the Filchner-Ronne Ice Shelf during the Quaternary. Second, the high radionuclide concentrations on bedrock surfaces, one of which is striated, suggest that some glacial landforms were created in at least Pliocene or more likely Miocene time. Third, the exceptionally low erosion rates imply that the modern cold, arid climate has persisted for millions of years. These findings provide evidence of old, stable landscapes over a wider area of Antarctica than the McMurdo Dry Valleys. Keywords: Shackleton Range, cosmogenic isotopes, geomorphology, ice-sheet change, erosion rates.

Published
2004

7. Drivers of abrupt Holocene shifts in West Antarctic ice stream direction determined from combined ice sheet modelling and geologic signatures

Author

Fogwill, C.J., Turney, C.S.M., Golledge, N.R., Rood, D.H., Hippe, K., Wacker, L., Wieler, R., Rainsley, E.B., Jones, R.S., Fogwill, C.J., Turney, C.S.M., Golledge, N.R., Rood, D.H., Hippe, K., Wacker, L., Wieler, R., Rainsley, E.B., and Jones, R.S.

Abstract

Determining the millennial-scale behaviour of marine-based sectors of the West Antarctic Ice Sheet (WAIS) is critical to improve predictions of the future contribution of Antarctica to sea level rise. Here high-resolution ice sheet modelling was combined with new terrestrial geological constraints (in situ 14C and 10Be analysis) to reconstruct the evolution of two major ice streams entering the Weddell Sea over 20 000 years. The results demonstrate how marked differences in ice flux at the marine margin of the expanded Antarctic ice sheet led to a major reorganization of ice streams in the Weddell Sea during the last deglaciation, resulting in the eastward migration of the Institute Ice Stream, triggering a significant regional change in ice sheet mass balance during the early to mid Holocene. The findings highlight how spatial variability in ice flow can cause marked changes in the pattern, flux and flow direction of ice streams on millennial timescales in this marine ice sheet setting. Given that this sector of the WAIS is assumed to be sensitive to ocean-forced instability and may be influenced by predicted twenty-first century ocean warming, our ability to model and predict abrupt and extensive ice stream diversions is key to a realistic assessment of future ice sheet sensitivity

Published
2017

9. Delayed maximum northern European summer temperatures during the Last Interglacial as a result of Greenland Ice Sheet melt

Author

Jones, R.t., Turney, C.s.m., Lang, B., Brooks, S.j., Rundgren, M., Hammarlund, D., Björck, S., Fogwill, C.j., Jones, R.t., Turney, C.s.m., Lang, B., Brooks, S.j., Rundgren, M., Hammarlund, D., Björck, S., and Fogwill, C.j.

Abstract

Here we report a new quantitative mean July temperature reconstruction using non-biting midges (chironomids) from the Danish Last Interglacial (LIG) site Hollerup (spanning 127-116 ka). We find that peak mean July temperatures of 17.5 degrees C, similar to those of the present day (1961-1990 CE), were reached shortly before the onset of the regional Carpinus pollen zone. Through comparison to terrestrial and marine sequences we demonstrate that peak summer warmth took place some three millennia after the onset of LIG warming in Europe, a marked delay in line with records from the North Atlantic. Crucially, the warmest northern European summer temperatures appear to follow maximum Greenland Ice Sheet mass loss, implying that meltwater substantially reduced Atlantic Meridional Overturning Circulation and depressed European temperatures during the early part of the interglacial.

Published
2016
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10. A multi-disciplinary perspective on climate model evaluation for Antarctica

Author

Bracegirdle, T.J., Bertler, N.A.N., Carleton, A.M., Ding, Q., Fogwill, C.J., Fyfe, J.C., Hellmer, H.H., Karpechko, A.Y., Kusahara, K., Larour, E., Mayewski, P.A., Meier, W.N., Polvani, L.M., Russell, J.L., Stevenson, S.L., Turner, J., van Wessem, J. M., van de Berg, W.J., Wainer, I., Bracegirdle, T.J., Bertler, N.A.N., Carleton, A.M., Ding, Q., Fogwill, C.J., Fyfe, J.C., Hellmer, H.H., Karpechko, A.Y., Kusahara, K., Larour, E., Mayewski, P.A., Meier, W.N., Polvani, L.M., Russell, J.L., Stevenson, S.L., Turner, J., van Wessem, J. M., van de Berg, W.J., and Wainer, I.

Published
2016

20. Cosmogenic nuclides 10Be and 26Al imply limited Antarctic Ice Sheet thickening and low erosion in the Shackleton Range for >1 m.y.

Author

Fogwill, C.J., Bentley, M.J., Sugden, D.E., Kerr, A.R., and Kubik, P.W.

Subjects
*NUCLIDES, *COSMOGONY, *ICE sheets, *EROSION, SHACKLETON Range (Antarctica)
Abstract

Concentrations of the cosmogenic nuclides 10Be and 26Al on bedrock surfaces in the Shackleton Range, Antarctica, indicate minimum exposure ages between 3.0 ± 0.3 and 1.16 ± 0.10 Ma. The isotope data indicate that the maximum long-term erosion rate is 0.10-0.35 m/m.y., and the ratios suggest no prolonged periods of burial by cold-based ice. The findings are important because of the location of the massif close to the junction of the East Antarctic Ice Sheet and the landward extent of the Filchner Ice Shelf. These results point to three conclusions. First, the massif has not been overridden by the East Antarctic Ice Sheet during the late Quaternary. Rather, moraines 200-340 m above outlet glaciers are likely to represent the maximum thickening of the Filchner-Ronne Ice Shelf during the Quaternary. Second, the high radionuclide concentrations on bedrock surfaces, one of which is striated, suggest that some glacial landforms were created in at least Pliocene or more likely Miocene time. Third, the exceptionally Iow erosion rates imply that the modern cold, arid climate has persisted for millions of years. These findings provide evidence of old, stable landscapes over a wider area of Antarctica than the McMurdo Dry Valleys. [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
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21. Drivers of abrupt Holocene shifts in West Antarctic ice stream direction determined from combined ice sheet modelling and geologic signatures

Author

Fogwill, C.J., Turney, C.S.M., Golledge, N.R., Rood, D.H., Hippe, K., Wacker, L., Wieler, R., Rainsley, E.B., Jones, R.S., Fogwill, C.J., Turney, C.S.M., Golledge, N.R., Rood, D.H., Hippe, K., Wacker, L., Wieler, R., Rainsley, E.B., and Jones, R.S.

Abstract

Determining the millennial-scale behaviour of marine-based sectors of the West Antarctic Ice Sheet (WAIS) is critical to improve predictions of the future contribution of Antarctica to sea level rise. Here high-resolution ice sheet modelling was combined with new terrestrial geological constraints (in situ 14C and 10Be analysis) to reconstruct the evolution of two major ice streams entering the Weddell Sea over 20 000 years. The results demonstrate how marked differences in ice flux at the marine margin of the expanded Antarctic ice sheet led to a major reorganization of ice streams in the Weddell Sea during the last deglaciation, resulting in the eastward migration of the Institute Ice Stream, triggering a significant regional change in ice sheet mass balance during the early to mid Holocene. The findings highlight how spatial variability in ice flow can cause marked changes in the pattern, flux and flow direction of ice streams on millennial timescales in this marine ice sheet setting. Given that this sector of the WAIS is assumed to be sensitive to ocean-forced instability and may be influenced by predicted twenty-first century ocean warming, our ability to model and predict abrupt and extensive ice stream diversions is key to a realistic assessment of future ice sheet sensitivity

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