Influence of ice sheet topography on Greenland precipitation during the Eemian interglacial

AbstractDetailed digital elevation models (DEMs) do not exist for much of the Greenland and Antartic ice sheets. Radar altimetry is at present the primary, in many cases the only, source of topographic data over the ice sheets, but the horizontal resolution of such data is coarse. Satellite-radar interferometry uses the phase difference between pairs of synthetic aperture radar (SAR) images to measure both ice-sheet topography and surface displacement. We have applied this technique using ERS-1 SAR data to make detailed (i.e. 80 m horizontal resolution) maps of surface topography in a 100 km by 300 km strip in West Greenland, extending northward from just above Jakobshavns Isbræ. Comparison with а 76 km long line of airborne laser-altimeter data shows that We have achieved a relative accuracy of 2.5 m along the profile. These observations provide a detailed view of dynamically Supported topography near the margin of an ice sheet. In the final section We compare our estimate of topography with phase contours due to motion, and confirm our earlier analysis concerning vertical ice-sheet motion and complexity in ERS-1 SAR interferograms.

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How warm was Greenland during the last interglacial period?

Climate of the Past ◽

10.5194/cp-12-1933-2016 ◽

2016 ◽

Vol 12 (9) ◽

pp. 1933-1948 ◽

Cited By ~ 11

Author(s):

Amaelle Landais ◽

Valérie Masson-Delmotte ◽

Emilie Capron ◽

Petra M. Langebroek ◽

Pepijn Bakker ◽

...

Keyword(s):

Surface Temperature ◽

Ice Core ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Water Isotopes ◽

Interglacial Period ◽

Last Interglacial ◽

Last Interglacial Period ◽

Ice Sheet Topography ◽

North Greenland

Abstract. The last interglacial period (LIG, ∼ 129–116 thousand years ago) provides the most recent case study of multimillennial polar warming above the preindustrial level and a response of the Greenland and Antarctic ice sheets to this warming, as well as a test bed for climate and ice sheet models. Past changes in Greenland ice sheet thickness and surface temperature during this period were recently derived from the North Greenland Eemian Ice Drilling (NEEM) ice core records, northwest Greenland. The NEEM paradox has emerged from an estimated large local warming above the preindustrial level (7.5 ± 1.8 °C at the deposition site 126 kyr ago without correction for any overall ice sheet altitude changes between the LIG and the preindustrial period) based on water isotopes, together with limited local ice thinning, suggesting more resilience of the real Greenland ice sheet than shown in some ice sheet models. Here, we provide an independent assessment of the average LIG Greenland surface warming using ice core air isotopic composition (δ15N) and relationships between accumulation rate and temperature. The LIG surface temperature at the upstream NEEM deposition site without ice sheet altitude correction is estimated to be warmer by +8.5 ± 2.5 °C compared to the preindustrial period. This temperature estimate is consistent with the 7.5 ± 1.8 °C warming initially determined from NEEM water isotopes but at the upper end of the preindustrial period to LIG temperature difference of +5.2 ± 2.3 °C obtained at the NGRIP (North Greenland Ice Core Project) site by the same method. Climate simulations performed with present-day ice sheet topography lead in general to a warming smaller than reconstructed, but sensitivity tests show that larger amplitudes (up to 5 °C) are produced in response to prescribed changes in sea ice extent and ice sheet topography.

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Satellite Laser Altimeter for Measurement of Ice Sheet Topography

IEEE Transactions on Geoscience and Remote Sensing ◽

10.1109/tgrs.1982.350423 ◽

1982 ◽

Vol GE-20 (4) ◽

pp. 544-549 ◽

Cited By ~ 9

Author(s):

Jack L. Bufton ◽

John E. Robinson ◽

Michael D. Femiano ◽

Fred S. Flatow

Keyword(s):

Ice Sheet ◽

Laser Altimeter ◽

Ice Sheet Topography

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Antarctic Ice-Sheet Topography and Surface-Bedrock Relationships

Annals of Glaciology ◽

10.1017/s0260305500001282 ◽

1986 ◽

Vol 8 ◽

pp. 124-128 ◽

Cited By ~ 14

Author(s):

N.F. McIntyre

Keyword(s):

Three Dimensional ◽

Ice Sheet ◽

Coastal Regions ◽

Three Dimensional Flow ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Dimensional Flow ◽

Ice Velocity ◽

The Antarctic ◽

Ice Sheet Topography

Mapping the topography of the Antarctic ice sheet has confirmed that there is, typically, a decrease in the wavelength and increase in the amplitude of surface undulations with distance from ice divides. This pattern is distorted by converging ice flow in coastal regions and by other variations in subglacial relief, ice velocity, and viscosity. The near-symmetry of undulations indicates the extent of three-dimensional flow over bedrock peaks. Spectral analyses indicate the greater response of the ice sheet to bedrock features with longer wavelengths. This is affected, and in some cases dominated, by the inhomogeneous and non-isothermal nature of the ice sheet.

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Sensitivity experiments to sea surface temperatures, sea-ice extent and ice-sheet reconstruction, for the Last Glacial Maximum

Annals of Glaciology ◽

10.1017/s0260305500016049 ◽

1995 ◽

Vol 21 ◽

pp. 343-347 ◽

Cited By ~ 9

Author(s):

G. Ramstein ◽

S. Joussaume

Keyword(s):

Sea Ice ◽

Last Glacial Maximum ◽

Ice Sheet ◽

Sea Surface ◽

Sea Surface Temperatures ◽

Sea Ice Extent ◽

The Impact ◽

The Last Glacial Maximum ◽

Ice Sheet Topography ◽

The Last Glacial

For the Last Glacial Maximum, (LGM; 21 000 BP), simulations using atmospheric general-circulation models (AGCMs) are very sensitive to the prescribed boundary conditions. Most of the recent numerical experiments have used the CLIMAP (1981) data set for ice-sheet topography, sea-ice extent and sea surface temperatures (SSTs). To demonstrate the impact of ice-sheet reconstruction on the LGM climate, we performed two simulations: one using CLIMAP (1981) ice-sheet topography, the other using the new reconstruction provided by Peltier. We show that, although the geographical structure of the annually averaged temperature is not modified, there are important seasonal and regional impacts on the temperature distribution. In a second step, to analyze the effects of cooler SSTs and sea-ice extent, we performed a simulation using CLIMAP (1981) for the ice-sheet topography, but with present SSTs. We find that the cooling due to ice sheets for the LGM climate is one-third of the global annually averaged cooling, and dial the southward shift of the North Atlantic low in winter is not due to sea-ice extent, but is an orographic effect due to the Laurenride ice sheet. This set of sensitivity experiments allows us also to discriminate between thermal and orographic forcings and to show the impact of the ice-sheet topography and cooler SSTs on the pattern of planetary waves during the LGM climate.

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Sensitivity of a Two-Layer Model Atmosphere to Changes in Ice-Sheet Topography

Annals of Glaciology ◽

10.1017/s0260305500014129 ◽

1997 ◽

Vol 25 ◽

pp. 246-249 ◽

Cited By ~ 1

Author(s):

Charles S. Jackson

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Model Atmosphere ◽

Hudson Bay ◽

Surprising Result ◽

Layer Model ◽

The North ◽

Two Layer Model ◽

The North Atlantic ◽

Ice Sheet Topography

Results are presented testing the sensitivity of a two-layer model to changes in the Laurentide ice sheet’s geometry following the collapse of the Hudson Bay ice dome. Since the ice sheet is thought to induce cooling over the North Atlantic through its mechanical effect on atmospheric circulation, the model shows a surprising result in that the removal of the Hudson Bay ice dome led to a further cooling of 4°C over the North Atlantic. This finding suggests that fluctuations in ice-sheet topography could have contributed to the climate variability witnessed in the geologic record. Further study is needed to understand the mechanism behind these results.

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