Oxygen 18/16 variability in Greenland snow and ice with 10−3- to 105-year time resolution

摘要: The 3-km-long Greenland Ice Sheet Project 2 (GISP2) ice core presents a 100,000 +- year detailed oxygen isotope profile covering almost full glacial-interglacial cycle. Measuranents of isotopic fluctuations in snow, frost, and atmospheric water vapor samples collected during summer field seasons (up to 20%0) are compatible with the large abrupt 80/160 changes observed accumulated tim. Snow pit 1580 profiles from GISP2 summit area, however, show rapid smoothing 180/160 signal near surface. Beyond about 2-m depth smoothedi5180 is fairly well preserved can be interpreted terms average local weather conditions climate. longer climate also have regional often global significance. In older part record, corresponding marine stages (MIS) 5a 5d, effect orbital forcing via 19- 23-kyr precession cycles 41-kyr obliquity cycle obvious. From end ofMIS 5a, at 75,000 years B.P., till glacial Younger Dryas-Preboreal transition, 11,650 O180/160 record shows frequent, switches between intermediate interstadial low stadial values. Fourier spectra oscillations that superimposed on orbitally induced contain strong periodicity 1.5 kyr, broad peak 4.0 additional shorter periods. Detailed comparison Vostok, Antarctica, 15D record; Pacific Ocean foraminiferal 180/160; Grande Pile, France, tree pollen; insolation indicates counterpart many found other records, clearly expression worldwide extent. Correlation events independent SPECMAP time scales for interval 10,000-50,000 B.P. excellent chronometric agreement, except possibly event labeled 3.1. interglacial transition evidently started simultaneously Arctic Antarctic, but its development isotopes was later suppressed by influence meltwater, especially Barents Sea sheet, deep formation ocean circulation. Meltwaters different sheets bordering North Atlantic influenced circulation Bolling-Allerod complex Dryas led distinct European Holocene long-term stable mean values contains several fluauations periods millennia. Dominant 6.3-year oscillation amplitude up 3 4%0. Periodicities 11 210 years, solar-modulated records cosmogenic 1oBe 14C, suggest solar processes as cause these cycles. Depression of180/160 (cooling) volcanic eruptions stacked GISP21580 small not likely trigger major changes.