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692 results on '"Alley, Richard B."'

159. North Atlantic climate variability from a self-organizing map perspective

Author

Reusch, David B, Alley, Richard B, Hewitson, Bruce C, Department of Environmental and Geographical Science, and Faculty of Science

Subjects
Monopole, Dynamical climatology, Non linear system, Winter, North Atlantic, Mean sea level, subtropical zone, Position, Système non linéaire, Sea level pressure, Monopôle, Analyse composante principale, Europe, monthly average, Occurrence frequency, Atlantic Ocean Islands, Dipôle, principal components analysis, North Atlantic oscillation, trend-surface analysis, Dipole, Self-organising feature maps, Zone subtropicale, Atlantic Ocean, Azores
Abstract

[1] North Atlantic variability in general, and the North Atlantic Oscillation (NAO) in particular, is a long-studied, very important but still not well-understood problem in climatology. The recent trend to a higher wintertime NAO index was accompanied by an additional increase in the Azores High not coupled to changes in the Icelandic Low, as shown by a self-organizing maps (SOMs) analysis of monthly mean DJF mean sea level pressure data from 1957 to 2002. SOMs are a nonlinear tool to optimally extract a user-specified number of patterns or icons from an input data set and to uniquely relate any input data field to an icon, allowing analyses of occurrence frequencies and transitions complementary to principal component analysis (PCA). SOMs analysis of ERA-40 data finds a North Atlantic monopole roughly colocated with the mean position of the Azores High, as well as the well-known NAO dipole involving the Icelandic Low and the subtropical high. Little trend is shown in December, but the Azores High increased along with the NAO in January and February over the study interval, with implications for storminess in northwestern Europe. In short, our SOM-based analyses of winter MSLP have both confirmed prior knowledge and expanded it through the relative ease of use and power with nonlinear systems of the SOM-based approach to climatological analysis.

Published
2007
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160. Summary for Policymakers

Author

Alley, Richard B., Berntsen, Terje, Bindoff, Nathaniel, Chidthaisong, Amnat, Friedlingstein, Pierre, Gregory, Jonathan, Hegerl, Gabriele, Heimann, Martin, Hewitson, Bruce, Hoskins, Brian, Joos, Fortunat, Jouzel, Jean, Kattsov, Vladimir, Lohmann, Ulrike, Manning, Martin, Matsuno, Taroh, Molina, Mario, Nicholls, Neville, Overpeck, Jonathan, Qin, Dahe, Raga, Graciela, Ramaswamy, Venkatachalam, Ren, Jiawen, Rusticucci, Matilde, Solomon, Susan, Somerville, Richard, Stocker, Thomas, Stott, Peter, Stouffer, Ronald, Whetton, Penny, Wood, Richard, Wratt, David, Arblaster, J., Brasseur, G., Christensen, J.H., Denman, K.L., Fahey, D.W., Forster, P., Jansen, E., Jones, P.D., Knutti, R., Le Treut, H, Lemke, P., Meehl, G., Mote, P., Randall, D.A., Stone, D.A., Trenberth, K.E., Willebrand, J., Zwiers, F., Chen, Zhenlin, Marquis, M, Averyt, K, Tignor, M, Miller, H, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2007

162. On thickening ice? (Perspectives: Climate Change)

Author

Alley, Richard B.

Subjects
Glaciology -- Research -- Environmental aspects, Global temperature changes -- Causes of -- Research -- Environmental aspects, Climatology -- Research -- Environmental aspects, Ice sheets -- Environmental aspects -- Research, Science and technology, Research, Causes of, Environmental aspects
Abstract

The big ice sheets in Greenland and Antarctica are key elements of the global climate system. By storing large volumes of water as ice or ice-contact lakes and sometimes releasing [...]

Published
2002

165. Implications of abrupt climate change

Author

Alley, Richard B.

Subjects
Greenhouse Effect, Time Factors, Climate, Humans, International Agencies, sense organs, skin and connective tissue diseases, Models, Biological, Ecosystem, Research Article
Abstract

Records of past climates contained in ice cores, ocean sediments, and other archives show that large, abrupt, widespread climate changes have occurred repeatedly in the past. These changes were especially prominent during the cooling into and warming out of the last ice age, but persisted into the modern warm interval. Changes have especially affected water availability in warm regions and temperature in cold regions, but have affected almost all climatic variables across much or all of the Earth. Impacts of climate changes are smaller if the changes are slower or more-expected. The rapidity of abrupt climate changes, together with the difficulty of predicting such changes, means that impacts on the health of humans, economies and ecosystems will be larger if abrupt climate changes occur. Most projections of future climate include only gradual changes, whereas paleoclimatic data plus models indicate that abrupt changes remain possible; thus, policy is being made based on a view of the future that may be optimistic.

Published
2004

167. Physical properties of the WAIS Divide ice core

Author

Fitzpatrick, Joan J., primary, Voigt, Donald E., additional, Fegyveresi, John M., additional, Stevens, Nathan T., additional, Spencer, Matthew K., additional, Cole-Dai, Jihong, additional, Alley, Richard B., additional, Jardine, Gabriella E., additional, Cravens, Eric D., additional, Wilen, Lawrence A., additional, Fudge, T.J., additional, and Mcconnell, Joseph R., additional

Published
2014
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170. Tidally controlled stick-slip discharge of aWest Antarctic Ice

Author

King, Matt A., Padman, Laurence, Alley, Richard B., Bindschadler, Robert A., and Anandakrishnan, Sridhar

Abstract

A major West Antarctic ice stream discharges by sudden and brief periods of very rapid motion paced by oceanic tidal oscillations of about 1 meter. Acceleration to speeds greater than 1 meter per hour and deceleration back to a stationary state occur in minutes or less. Slip propagates at approximately 88 meters per second, suggestive of a shear wave traveling within the subglacial till. A model of an episodically slipping friction-locked fault reproduces the observed quasi-periodic event timing, demonstrating an ice stream's ability to change speed rapidly and its extreme sensitivity to subglacial conditions and variations in sea level. Flow of an Antarctic ice stream abruptly waxes and wanes in response to daily tides, implying that the forces pushing and resisting it are delicately balanced. Flow of an Antarctic ice stream abruptly waxes and wanes in response to daily tides, implying that the forces pushing and resisting it are delicately balanced.

Published
2003

171. Ice sheet grounding zone stabilization due to till compaction

Author

Christianson, Knut, primary, Parizek, Byron R., additional, Alley, Richard B., additional, Horgan, Huw J., additional, Jacobel, Robert W., additional, Anandakrishnan, Sridhar, additional, Keisling, Benjamin A., additional, Craig, Brian D., additional, and Muto, Atsuhiro, additional

Published
2013
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173. Icing the North Atlantic

Author

Alley, Richard B.

Subjects
North Atlantic region -- Natural history, Drift -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Some of the large climate changes in the North Atlantic could have been caused by the advance and retreat of the Laurentide, one of the great ice sheets feeding the region. New research indicates that the ice-rafted-debris signal of the youngest Heinrich event, which took place around 17,000 years ago, is more consistent with a complex and varied reaction to a surge in this ice sheet than with a common reaction of ice masses to an external forcing. This research reopens the debate about the meaning of ice-rafted-debris deposits and of the north-south phasing of deglaciation.

Published
1998

181. The role of channelized basal melt in ice-shelf stability: recent progress and future priorities.

Author

Alley, Karen E., Scambos, Ted A., and Alley, Richard B.

Subjects
*ICE shelves, *ANTARCTIC ice, *SEAWATER, *STRUCTURAL stability, *MELTING, *MELTWATER
Abstract

Basal channels, which form where buoyant plumes of ocean water and meltwater carve troughs upwards into ice-shelf bases, are widespread on Antarctic ice shelves. The formation of these features modulates ice-shelf basal melt by influencing the flow of buoyant plumes, and influences structural stability through concentration of strain and interactions with fractures. Because of these effects, and because basal channels can change rapidly, on timescales similar to those of ice-shelf evolution, constraining the impacts of basal channels on ice shelves is necessary for predicting future ice-shelf destabilization and retreat. We suggest that future research priorities should include constraining patterns and rates of basal channel change, determining mechanisms and detailed patterns of basal melt, and quantifying the influence that channel-related fractures have on ice-shelf stability. [ABSTRACT FROM AUTHOR]

Published
2023
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186. Greenland was nearly ice-free for extended periods during the Pleistocene

Author

Schaefer, Joerg M., Finkel, Robert C., Balco, Greg, Alley, Richard B., Caffee, Marc W., Briner, Jason P., Young, Nicolas E., Gow, Anthony J., and Schwartz, Roseanne

Abstract

The Greenland Ice Sheet (GIS) contains the equivalent of 7.4 metres of global sea-level rise. Its stability in our warming climate is therefore a pressing concern. However, the sparse proxy evidence of the palaeo-stability of the GIS means that its history is controversial (compare refs 2 and 3 to ref. 4). Here we show that Greenland was deglaciated for extended periods during the Pleistocene epoch (from 2.6 million years ago to 11,700 years ago), based on new measurements of cosmic-ray-produced beryllium and aluminium isotopes (10Be and 26Al) in a bedrock core from beneath an ice core near the GIS summit. Models indicate that when this bedrock site is ice-free, any remaining ice is concentrated in the eastern Greenland highlands and the GIS is reduced to less than ten per cent of its current volume. Our results narrow the spectrum of possible GIS histories: the longest period of stability of the present ice sheet that is consistent with the measurements is 1.1 million years, assuming that this was preceded by more than 280,000 years of ice-free conditions. Other scenarios, in which Greenland was ice-free during any or all Pleistocene interglacials, may be more realistic. Our observations are incompatible with most existing model simulations that present a continuously existing Pleistocene GIS. Future simulations of the GIS should take into account that Greenland was nearly ice-free for extended periods under Pleistocene climate forcing.

Published
2016
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189. Geological record of ice shelf break-up and grounding line retreat, Pine Island Bay, West Antarctica

Author

Jakobsson, Martin, primary, Anderson, John B., additional, Nitsche, Frank O., additional, Dowdeswell, Julian A., additional, Gyllencreutz, Richard, additional, Kirchner, Nina, additional, Mohammad, Rezwan, additional, O'Regan, Matthew, additional, Alley, Richard B., additional, Anandakrishnan, Sridhar, additional, Eriksson, Björn, additional, Kirshner, Alexandra, additional, Fernandez, Rodrigo, additional, Stolldorf, Travis, additional, Minzoni, Rebecca, additional, and Majewski, Wojciech, additional

Published
2011
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193. Past rates of climate change in the Arctic

Author

White, James W.C., primary, Alley, Richard B., additional, Brigham-Grette, Julie, additional, Fitzpatrick, Joan J., additional, Jennings, Anne E., additional, Johnsen, Sigfus J., additional, Miller, Gifford H., additional, Steven Nerem, R., additional, and Polyak, Leonid, additional

Published
2010
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194. History of sea ice in the Arctic

Author

Polyak, Leonid, primary, Alley, Richard B., additional, Andrews, John T., additional, Brigham-Grette, Julie, additional, Cronin, Thomas M., additional, Darby, Dennis A., additional, Dyke, Arthur S., additional, Fitzpatrick, Joan J., additional, Funder, Svend, additional, Holland, Marika, additional, Jennings, Anne E., additional, Miller, Gifford H., additional, O'Regan, Matt, additional, Savelle, James, additional, Serreze, Mark, additional, St. John, Kristen, additional, White, James W.C., additional, and Wolff, Eric, additional

Published
2010
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196. History of the Greenland Ice Sheet: paleoclimatic insights

Author

Alley, Richard B., primary, Andrews, J.T., additional, Brigham-Grette, J., additional, Clarke, G.K.C., additional, Cuffey, K.M., additional, Fitzpatrick, J.J., additional, Funder, S., additional, Marshall, S.J., additional, Miller, G.H., additional, Mitrovica, J.X., additional, Muhs, D.R., additional, Otto-Bliesner, B.L., additional, Polyak, L., additional, and White, J.W.C., additional

Published
2010
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