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Quantifying the Jakobshavn Effect: Jakobshavn Isbrae, Greenland, Compared to Byrd Glacier, Antarctica : Volume 8, Issue 2 (25/04/2014)

By Hughes, T.

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Book Id: WPLBN0004023007
Format Type: PDF Article :
File Size: Pages 76
Reproduction Date: 2015

Title: Quantifying the Jakobshavn Effect: Jakobshavn Isbrae, Greenland, Compared to Byrd Glacier, Antarctica : Volume 8, Issue 2 (25/04/2014)  
Author: Hughes, T.
Volume: Vol. 8, Issue 2
Language: English
Subject: Science, Cryosphere, Discussions
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Historic
Publication Date:
2014
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

Citation

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Fastook, J., Sargent, A., Purdon, K., Yan, J., Hughes, T., Li, J., & Gogineni, S. (2014). Quantifying the Jakobshavn Effect: Jakobshavn Isbrae, Greenland, Compared to Byrd Glacier, Antarctica : Volume 8, Issue 2 (25/04/2014). Retrieved from http://nook-library.net/


Description
Description: School of Earth and Climate Sciences, Climate Change Institute, University of Maine, Orono, USA. The Jakobshavn Effect is a series of positive feedback mechanisms that was first observed on Jakobshavn Isbrae, which drains the west-central part of the Greenland Ice Sheet and enters Jakobshavn Isfjord at 69°10'. These mechanisms fall into two categories, reductions of ice-bed coupling beneath an ice stream due to surface meltwater reaching the bed, and reductions in ice-shelf buttressing beyond an ice stream due to disintegration of a laterally confined and locally pinned ice shelf. These uncoupling and unbuttressing mechanisms have recently taken place for Byrd Glacier in Antarctica and Jakobshavn Isbrae in Greenland, respectively. For Byrd Glacier, no surface meltwater reaches the bed. That water is supplied by drainage of two large subglacial lakes where East Antarctic ice converges strongly on Byrd Glacier. Results from modeling both mechanisms are presented here. We find that the Jakobshavn Effect is not active for Byrd Glacier, but is active for Jakobshavn Isbrae, at least for now. Our treatment is holistic in the sense it provides continuity from sheet flow to stream flow to shelf flow. It relies primarily on a force balance, so our results cannot be used to predict long-term behavior of these ice streams. The treatment uses geometrical representations of gravitational and resisting forces that provide a visual understanding of these forces, without involving partial differential equations and continuum mechanics. The Jakobshavn Effect was proposed to facilitate terminations of glaciation cycles during the Quaternary Ice Age by collapsing marine parts of ice sheets. This is unlikely for the Antarctic and Greenland ice sheets, based on our results for Byrd Glacier and Jakobshavn Isbrae, without drastic climate warming in high polar latitudes. Warming would affect other Antarctic ice streams already weakly buttressed or unbuttressed by an ice shelf. Ross Ice Shelf would still protect Byrd Glacier.

Summary
Quantifying the Jakobshavn Effect: Jakobshavn Isbrae, Greenland, compared to Byrd Glacier, Antarctica

Excerpt
Gagliardini, O., Durand, G., Zwinger, T., Hindmarsh, R. C. A., and Le Meur, E.: Coupling of ice-sheet melting and buttressing is a key process in ice-sheet dynamics, Geophys. Res. Lett., 37, L14501, doi:10.1029/2010GL043334, 2010.; Gow, A. J., Meese, D. A., Alley, R. B., Fitzpatrick, J. J., Anandakrishnan, S., Woods, G. A., and Elder, B. C.: Physical and structural properties of the Greenland Ice Sheet Project 2 ice cores: a review, J. Geophys. Res., 102, 26559–26575, 1997.; Greve, R.: A continuum-mechanical formulation for shallow polythermal ice sheets, Philos. T. Roy. Soc. A, 355, 921–974, doi:10.1098/rsta.1997.0050, 1997.; Hofstede, C. and Hughes, T.: Can ice sheets self-destruct and cause rapid climate change?, A case study: Jakobshavn Isbrae, Greenland, in: Atmosphre and Climate: Physics, Composition/Dynamis and Health Impacts, edited by: Wright, A. and Johnnson, S., Nova Science Publishers Inc., Hauppauge, NY, 1–33, 2013.; Holland, D. R., Thomas, R., de Young, B., Ribergaard, M., and Lyberth, B.: Acceleration of Jakobshavn Isbrae triggered by warm subsurface ocean waters, Nat. Geosci., 1, 659–664, doi:10.1038/ngeo316, 2008.; Hughes, T.: Ice Streamline Cooperative Antarctic Project, ISCAP Bulletin No. 1: Scientific Justification, Institute of Polar Studies, The Ohio State University, 1972.; Hughes, T.: Is the West Antarctic Ice Sheet disintegrating?, J. Geophys. Res., 78, 7884–7910, 1973.; Hughes, T.: A differential ablation-longitudinal compression mechanism for generating wave trains on cold alpine glaciers, in: Snow and Ice Symposium – Neiges et Glaces (Proceedings of the Moscow Symposium, August 1971, Actes du Colloque de Moscou, aout 1971), IASH – AISH Publication Number 104, 1975.; Hughes, T.: The Jakobshavns Effect, Geophys. Res. Lett., 13, 46–48, 1986.; Hughes, T.: On the pulling power of ice streams, J. Glaciol., 38, 125–151, 1992.; Hughes, T.: Ice Sheets, Oxford University Press, New York, 1998.; Rowden-Rich, R. J. M. and Wilson, C. J. L.: Models for strain localization in Law Dome, East Antarctica, Ann. Glaciol., 23, 396–401, 1996.; Hughes, T. J.: The geometrical force balance in glaciology, J. Geophys. Res., 108, NO.B11,2526, doi:10.1029/2003JB002557, 2003.; Hughes, T.: Variations of ice-bed coupling, beneath and beyond ice streams, J. Geophys. Res., 114, BO1410, doi:10.1029/2008JB005714, 2009.; Hughes, T.: A simple holistic hypothesis for the self-destruction of ice sheets, Quaternary Sci. Rev., 30, 1829–1845, 2011.; Hughes, T.: Holistic Ice Sheet Modeling: A First-Order Approach, Nova Science Publishers Inc., Hauppauge, New York, 2012.; Hughes, T., Sargent, A., and Fastook, J.: Ice-bed coupling beneath and beyond ice streams: Byrd Glacier, Antarctica, J. Geophys. Res., 116, 1–17, 2011.; Iken, A.: The effect of subglacial water pressure on the sliding velocity of a glacier in an idealized numerical model, J. Glaciol., 27, 407–422, 1981.; Iken, A. and Bindschadler, R. A.: Combined measurements of subglacial water pressure and surface velocity of Findelengletscher, Switzerland: conclusions about drainage system and sliding mechanism, J. Glaciol., 32, 101–119, 1986.; Iken, A., Echelmeyer, K., Harrison, W., and Funk, M.: Mechanics of fast flow in Jakobshavns Isbrae, West Greenland: Part I. measurements of temperature and water level in deep boreholes, J. Glaciol., 39, 15–25, 1993.; Jenson, J. W., Clark, P. U., MacAyeal, D. R., Ho, C. L., and Vela, J. C.: Numerical modeling of advective transport of saturated deforming sediment beneath the Lake Michigan Lobe, Laurentide Ice Sheet, Geomorphology, 14, 157–166, 1995.; Jenson, J. W., MacAyeal, D. R., Clark, P. U., Ho, C. L., and Vela, J. C.: Numerical modeling

 

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