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International Polar Year 2007–2008 - WMO

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to the ocean, which affects the global thermohaline<br />

circulation of the ocean. Airborne measurements<br />

with a radar capable of array processing in the crosstrack<br />

direction and synthetic aperture radar (SAR)<br />

processing in the along-track direction for sounding<br />

of ice and imaging the ice-bed interface, and scanning<br />

laser ranging (lidar), were planned to provide baseline<br />

measurements of the discharge of ice from outlet<br />

glaciers around the margin of the Greenland Ice Sheet.<br />

These measurements would also allow detection of<br />

elevation changes by comparison to earlier airborne<br />

missions and to satellites (CryoSat, ICESat). Automatic<br />

weather and mass balance stations were to be located<br />

on the ice in order to relate mass balance changes<br />

with meteorological conditions and to investigate<br />

the ablation processes in detail. In addition, the radar<br />

profiles would be used to map the melting under the<br />

ice in north Greenland and under the fast moving<br />

glaciers and ice streams, allowing inclusion of basal<br />

melt in the mass balance of the ice sheet. Traverses<br />

and field camps were proposed to collect GPS and<br />

geophysical data (magnetic, gravity), seismic profiles,<br />

and borehole logging and ice drilling along air survey<br />

routes. Combined with satellite data, they would be<br />

used to determine the crustal structure in Greenland<br />

and history of the sub-ice bedrock and sediments, and<br />

hence to map the heat flow and basal melt beneath the<br />

ice sheet. The dynamics of the ice stream Jakobshavn<br />

Isbrae, which has recently accelerated, was to be<br />

investigated using borehole instrumentation reaching<br />

to the base. Detailed studies of the response of ice<br />

dynamics in West Greenland to changes in surface<br />

melt through the penetration of runoff to the glacier<br />

bed were also proposed (Fig. 2.4-1).<br />

The North Eemian Ice Core Project (NEEM) was a<br />

major component of the overall work plan of “The<br />

Greenland Ice Sheet – Stability, History and Evolution”<br />

project. NEEM aimed at retrieving an ice core from<br />

northwest Greenland (77.45°N, 51.06°W) reaching<br />

back through the previous interglacial, the Eemian,<br />

during part of which the Arctic was warmer than the<br />

Holocene, thus offering an analogy for the conditions<br />

expected in the Arctic due to an anthropogenicallywarmed<br />

world. It was also hoped that the Holocene<br />

period from this deep ice core would provide a better<br />

isotopic record of the present climate than those from<br />

Fig. 2.4-1. Surface<br />

melt water<br />

penetrating the<br />

interior of the<br />

Greenland Ice Sheet<br />

via a moulin.<br />

(Photo: K. Steffen)<br />

s C I e n C e P r o g r a m 217

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