THE GISP2 DELTA-O-18 CLIMATE RECORD OF THE PAST 16,500 YEARS AND THE ROLE OF THE SUN, OCEAN, AND VOLCANOS

Measured O-18/O-16 ratios from the Greenland Ice Sheet Project 2 (GISP 2) ice core extending back to 16,500 cal yr B.P. provide a continuous record of climate change since the last glaciation, High-resolution an nual O-18/O-16 results were obtained for most of the current millenniu m (A.D. 818-1985) and record the Medieval Warm Period, the Little Ice Age, and a distinct 11-yr O-18/O-16 cycle, Volcanic aerosols depress c entral Greenland annual temperature (similar to 1.5 degrees C maximall y) and annual O-18/O-16 for about 4 yr after each major eruptive event , On a bidecadal to millennial time scale, the contribution of solar v ariability to Holocene Greenlandic temperature change is similar to 0. 4 degrees C. The role of thermohaline circulation change on climate, p roblematic during the Holocene, is more distinct for the 16,500-10,000 cal yr B.P. interval, (Analogous to C-14 age calibration terminology, we express time in calibrated (cal) yr B.P. (A.D. 1950 = 0 cal yr B.P .)). The Oldest Dryas/Bolling/Older Dryas/Allerod/Younger Dryas sequen ce appears in great detail, Bidecadal variance in O-18/O-16, bot not n ecessarily in temperature, is enhanced during the last phase of late-g lacial time and the Younger Dryas interval, suggesting switches of air mass transport between Set stream branches, The branched system is ne arly instantaneously replaced at the beginning of the Bolling and Holo cene (at similar to 14,670 and similar to 11,650 cal yr B.P., respecti vely) by an atmospheric circulation system in which O-18/O-16 and annu al accumulation initially track each other closely. Thermodynamic cons iderations of the accumulation rate-temperature relationship can be us ed to evaluate the O-18/O-16-temperature relationship, The GISP2 ice-l ayer-count years of major GISP2 climate transitions also support the u se of coral C-14 ages for age calibration. (C) 1995 University of Wash ington.