Pavlis, N. K., Holmes, S. A., Kenyon, S. C., and Factor, J. K., 2012.
The development and evaluation of the Earth Gravitational
Model 2008 (EGM2008). Journal of Geophysical Research,
117, B04406.
Smith, W. H. F., 1998. Seafloor tectonic fabric from satellite altimetry. Annual Reviews of Earth and Planetary Science, 26,
697–737.
Smith, W. H. F., and Sandwell, D. T., 1997. Global sea floor topography from satellite altimetry and ship depth soundings. Science,
277, 1956–1962.
Stacey, F. D., 1992. Physics of the Earth, 3rd edn. Kenmore: Brookfield Press.
Tapley, B. D., Born, G. H., and Parke, M. E., 1982. The Seasat
altimeter data and its accuracy assessment. Journal of Geophysical Research, 87, 3179–3188.
Torge, W., 1989. Gravimetry. Berlin: de Gruyter.
von Eötvös, R., 1919. Experimenteller Nachweis der
Schwereänderung, die ein auf normal geformter Erdoberfläche
in östlicher und westlicher Richtung bewegter Körper durch
diese Bewegung erleidet. Annalen der Physik, 59, 743–752,
Ser. 4.
Cross-references
Plate Tectonics
Technology in Marine Geosciences
GROUNDING LINE
Antoon Kuijpers and Tove Nielsen
Geological Survey of Denmark and Greenland (GEUS),
Copenhagen, Denmark
Definition
The grounding line, or more properly the grounding zone,
of glaciers and ice sheets is where their marine margins
cease to be in contact with the seafloor (Dowdeswell and
Fugelli, 2012).
A variety of features indicative of ice sheet and glacier
dynamics marks the grounding zone. These grounding
zone features indicate episodic rather than catastrophic
ice sheet retreat (Dowdeswell and Fugelli, 2012), but can
still yield important information on ice sheet and glacier
response to changes in climate and ocean temperature.
Observations of the Antarctic ice sheet show grounding
line retreat and ice shelf collapse at the Antarctic Peninsula
associated with warming in the Amundsen Sea (Payne
et al., 2004). Enhanced submarine melting at the grounding line has also been proposed as trigger mechanism for
recent acceleration of large, marine-based glaciers in
Greenland (Rignot et al., 2010). Modeling results confirm
how ocean warming and enhanced subglacial drainage
lead to increases in melting near the grounding line
(Jenkins, 2011). Ice sheet and glacier retreat leave grounding zone depositional systems on the seabed which
include ice-contact deltas and moraines and fans associated with subglacial and basal meltwater discharge
(Powell, 1990). At quasi-stable grounding lines, the fans
may grow to sea-level and form ice-contact deltas
(Seramur et al., 1997). Formation of the grounding
line features helps stabilization of the ice sheet in
protecting it from retreat driven by sea-level rise (Alley
et al., 2007).
Bibliography
Alley, R. B., Anandakrishnan, S., Dupont, T. K., Parizek, B. R., and
Pollard, D., 2007. Effect of sedimentation on ice sheet
grounding-line stability. Science, 315, 1838–1841.
Dowdeswell, J. A., Fugelli, E. M. G., 2012. The seismic architecture
and geometry of grounding-zone wedges formed at the marine
margins of past ice sheets. Geological Society of America Bulletin, doi:10.1130/B30628.1.
Jenkins, A., 2011. Convection-driven melting near the grounding
lines of ice shelves and tidewater glaciers. Journal of Physical
Oceanography, 41, 2279–2294.
Payne, A. J., Vieli, A., Sheperd, A. P., Wingham, D. J., and Rignot,
E. J., 2004. Recent dramatic thinning of the largest West Antarctic ice stream triggered by oceans. Geophysical Research Letters, 31, L23401, doi:10.1029/2004GL021284.
Powell, R. D., 1990. Glacimarine processes at grounding-line fans
and their growth to ice-contact deltas. In Special Publications.
London: Geological Society, Vol. 53, Glaciomarine Environments: Processes and Sediments ( J.A. Dowdeswell, J.D.
Scourse, Eds.), pp. 53–73.
Rignot, E. J., Xu, Y., Koppes, M. N., Menemenlis, D., Schodlok,
M., Spreen, G., 2010. Submarine melting at the grounding line
of Greenland’s tidewater glaciers: observations and implications. In Abstracts AGU Fall Meeting 2010. American Geophysical Union, Abstract #C12B-07R.
Seramur, K. C., Powell, R. D., and Carlson, P. R., 1997. Evaluation
of conditions along the grounding line of temperate marine glaciers: an example from Muir Inlet, Glacier Bay, Alaska. Marine
Geology, 140, 307–328.
Cross-references
Currents
Eustasy
Fjords
Ice-rafted Debris (IRD)
Moraines
Paleoceanography
Regional Marine Geology
Sea-Level
Sediment Dynamics
Sediment Transport Models
Shelf
GUYOT, ATOLL
Eberhard Gischler
Institute of Geosciences, Johann Wolfgang Goethe
University, Frankfurt am Main, Germany
Definition
Atolls are circular- to irregular-shaped, isolated oceanic
reef structures at or near sea-level that enclose a lagoon
302
GROUNDING LINE
The development and evaluation of the Earth Gravitational
Model 2008 (EGM2008). Journal of Geophysical Research,
117, B04406.
Smith, W. H. F., 1998. Seafloor tectonic fabric from satellite altimetry. Annual Reviews of Earth and Planetary Science, 26,
697–737.
Smith, W. H. F., and Sandwell, D. T., 1997. Global sea floor topography from satellite altimetry and ship depth soundings. Science,
277, 1956–1962.
Stacey, F. D., 1992. Physics of the Earth, 3rd edn. Kenmore: Brookfield Press.
Tapley, B. D., Born, G. H., and Parke, M. E., 1982. The Seasat
altimeter data and its accuracy assessment. Journal of Geophysical Research, 87, 3179–3188.
Torge, W., 1989. Gravimetry. Berlin: de Gruyter.
von Eötvös, R., 1919. Experimenteller Nachweis der
Schwereänderung, die ein auf normal geformter Erdoberfläche
in östlicher und westlicher Richtung bewegter Körper durch
diese Bewegung erleidet. Annalen der Physik, 59, 743–752,
Ser. 4.
Cross-references
Plate Tectonics
Technology in Marine Geosciences
GROUNDING LINE
Antoon Kuijpers and Tove Nielsen
Geological Survey of Denmark and Greenland (GEUS),
Copenhagen, Denmark
Definition
The grounding line, or more properly the grounding zone,
of glaciers and ice sheets is where their marine margins
cease to be in contact with the seafloor (Dowdeswell and
Fugelli, 2012).
A variety of features indicative of ice sheet and glacier
dynamics marks the grounding zone. These grounding
zone features indicate episodic rather than catastrophic
ice sheet retreat (Dowdeswell and Fugelli, 2012), but can
still yield important information on ice sheet and glacier
response to changes in climate and ocean temperature.
Observations of the Antarctic ice sheet show grounding
line retreat and ice shelf collapse at the Antarctic Peninsula
associated with warming in the Amundsen Sea (Payne
et al., 2004). Enhanced submarine melting at the grounding line has also been proposed as trigger mechanism for
recent acceleration of large, marine-based glaciers in
Greenland (Rignot et al., 2010). Modeling results confirm
how ocean warming and enhanced subglacial drainage
lead to increases in melting near the grounding line
(Jenkins, 2011). Ice sheet and glacier retreat leave grounding zone depositional systems on the seabed which
include ice-contact deltas and moraines and fans associated with subglacial and basal meltwater discharge
(Powell, 1990). At quasi-stable grounding lines, the fans
may grow to sea-level and form ice-contact deltas
(Seramur et al., 1997). Formation of the grounding
line features helps stabilization of the ice sheet in
protecting it from retreat driven by sea-level rise (Alley
et al., 2007).
Bibliography
Alley, R. B., Anandakrishnan, S., Dupont, T. K., Parizek, B. R., and
Pollard, D., 2007. Effect of sedimentation on ice sheet
grounding-line stability. Science, 315, 1838–1841.
Dowdeswell, J. A., Fugelli, E. M. G., 2012. The seismic architecture
and geometry of grounding-zone wedges formed at the marine
margins of past ice sheets. Geological Society of America Bulletin, doi:10.1130/B30628.1.
Jenkins, A., 2011. Convection-driven melting near the grounding
lines of ice shelves and tidewater glaciers. Journal of Physical
Oceanography, 41, 2279–2294.
Payne, A. J., Vieli, A., Sheperd, A. P., Wingham, D. J., and Rignot,
E. J., 2004. Recent dramatic thinning of the largest West Antarctic ice stream triggered by oceans. Geophysical Research Letters, 31, L23401, doi:10.1029/2004GL021284.
Powell, R. D., 1990. Glacimarine processes at grounding-line fans
and their growth to ice-contact deltas. In Special Publications.
London: Geological Society, Vol. 53, Glaciomarine Environments: Processes and Sediments ( J.A. Dowdeswell, J.D.
Scourse, Eds.), pp. 53–73.
Rignot, E. J., Xu, Y., Koppes, M. N., Menemenlis, D., Schodlok,
M., Spreen, G., 2010. Submarine melting at the grounding line
of Greenland’s tidewater glaciers: observations and implications. In Abstracts AGU Fall Meeting 2010. American Geophysical Union, Abstract #C12B-07R.
Seramur, K. C., Powell, R. D., and Carlson, P. R., 1997. Evaluation
of conditions along the grounding line of temperate marine glaciers: an example from Muir Inlet, Glacier Bay, Alaska. Marine
Geology, 140, 307–328.
Cross-references
Currents
Eustasy
Fjords
Ice-rafted Debris (IRD)
Moraines
Paleoceanography
Regional Marine Geology
Sea-Level
Sediment Dynamics
Sediment Transport Models
Shelf
GUYOT, ATOLL
Eberhard Gischler
Institute of Geosciences, Johann Wolfgang Goethe
University, Frankfurt am Main, Germany
Definition
Atolls are circular- to irregular-shaped, isolated oceanic
reef structures at or near sea-level that enclose a lagoon
302
GROUNDING LINE