Spatial and temporal oxygen isotope variability in northern Greenland –implications for a new climate record over the past millennium

摘要

We present for the first time all 12 δ18O records obtained fromice cores drilled in the framework of the North Greenland Traverse (NGT)between 1993 and 1995 in northern Greenland. The cores cover an area of 680?km??×??317?km,10?% of the Greenland ice sheet. Depending on core length(100–175?m) and accumulation rate (90–200?kg?m?2?a?1) the singlerecords reflect an isotope–temperature history over the last 500–1100 years.Lowest δ18O mean values occur north of the summit and east of themain divide as a consequence of Greenland's topography. In general, icecores drilled on the main ice divide show different results than thosedrilled east of the main ice divide that might be influenced by secondaryregional moisture sources.A stack of all NGT records and the NGRIP record is presented with improvedsignal-to-noise ratio. Compared to single records, this stack represents themean δ18O signal for northern Greenland that is interpreted asproxy for temperature. Our northern Greenland δ18O stackindicates distinctly enriched δ18O values during medievaltimes, about AD?1420?±?20 and from AD?1870 onwards. The period betweenAD?1420 and AD?1850 has depleted δ18O values compared to theaverage for the entire millennium and represents the Little Ice Age. Theδ18O values of the 20th century are comparable to themedieval period but are lower than that about AD?1420.