Greenland ice core dating
Abrupt changes are of great concern for those who model future changes in climate and their potential impacts on society.Ice cores record millennia of ancient snowfalls, which gradually turned to crystalline glacier ice.The record for the longest span of time recorded is found at Vostok, high on the Antarctic ice sheet, possibly extending back 400,000 years.Dating of such records, however, must be done indirectly by correlating them to other records, such as marine oxygen isotope stages, meltwater pulses seen in sea-level curves, or pollen.Our editors will review what you’ve submitted and determine whether to revise the article.Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work!These cores span about 110,000 years of relatively stable ice.Comparison between GRIP and GISP-2, however, shows that the lowest 100–150 metres (330–490 feet), which date from 110,000 to perhaps 250,000 years ago, do not correlate and are most likely distorted by movement of the accumulation in polar-desert conditions precludes counting, but the longest records are obtained here.
Coring of mountain glaciers in tropical and subtropical areas must be kept from melting.
Helicopters are sometimes available, but often it is necessary to pack the cores in boxes of dry ice and bring them down to waiting trucks.
H) that come directly from the water of ancient snows.
In areas of high accumulation, such as low-latitude mountain glaciers and the Greenland Ice Sheet, annual layers of ice representing tens of thousands of years can be seen and counted, often with the unaided eye.
The first deep drilling took place in the 1960s as preliminary efforts at Camp Century, Greenland, and Byrd Station, Antarctica.
The chemistry of the ash can often be tied directly to known volcanoes or ash layers in sediment.