1. Unit 10 - Ice Core Dating Going to Greenland: Some Pictures from the Longest Annually Counted Climate Record Yet Produced (all photos by R. Alley)

2. Unit 10 - Ice Core Dating Dr. Alley, at a slightly younger age, enjoying one of the comforts of home after a few weeks without showers working on the ice sheet as part of a US National Science Foundation-funded project.

3. Unit 10 - Ice Core Dating A good day in Greenland. The newspapers (left), although over a month old, are functional (see upper right).

4. Unit 10 - Ice Core Dating A bad day in Greenland. ‘Nuff said.

5. Unit 10 - Ice Core Dating All the comforts of home on two miles of ice--golf, volleyball, and freeze-dried laundry.

6. Unit 10 - Ice Core Dating Richard Alley (with ski goggles, without shirt) and Joan Fitzpatrick dig the second of adjacent snow pits. A roof is placed on one side, light shines into the other side and through the wall to illuminate the strata.

7. Unit 10 - Ice Core Dating Close-up of about 6-inch-wide piece of intervening wall in previous picture. Snow is blue for the same reason the ocean is--red is soaked up. Wind-packed layers appear darker; sun-cooked layers appear lighter.

8. Unit 10 - Ice Core Dating The whole two-meter (six-foot) high wall of the snow pit in the previous pictures, central Greenland, dug in late spring. Summer layers lost mass when warmed by the sun (but not melted), and so appear lighter in color. The sun does not shine in the winter, so those layers all appear dark. There is a trend to darker layers downward, because of compaction under the weight of more snow, and because less light gets deep. Previous summer Summer before that And summer before that A few of the many layers from single storms.

9. Unit 10 - Ice Core Dating Assembling the drill tower (left), and the midnight sun over the tower (right). The dome kept bad weather off the drillers. The tower was 100 feet high.

10. Unit 10 - Ice Core Dating Katherine, from Alaska, on the big National Science Foundation/Polar Ice Coring Office deep drill in central Greenland. It takes a big drill to extract cores all the way to the bottom of a two- mile thick ice sheet.

11. Unit 10 - Ice Core Dating Bill Kimball, University of New Hampshire, cutting ice cores for examination in undersnow laboratory, central Greenland.

12. Unit 10 - Ice Core Dating Ice cores awaiting analysis in central Greenland. The notation “1547” on the end of one of the core trays indicates a depth of 1547 m, or almost 1 mile.

13. Unit 10 - Ice Core Dating Kurt Cuffey (then a Penn State undergraduate, now a world-renowned professor at the University of California- Berkeley) examines an ice core in central Greenland. Kurt’s annual-layer counts were among those used to establish the age of the Greenland ice core, and the reproducibility of counts by different observers.

14. Unit 10 - Ice Core Dating Ice core on light table, central Greenland. Depths of 1411.8 m and 1411.9 m (slightly less than a mile) are noted. The mass-loss summer layers have made bigger-bubbled layers that appear dark here (blue bars), and compaction and ice flow have moved the layers closer together. These are about 8400 years old.