Historically, stable isotope ratios in ice cores from polar regions (18O/16O and D/H ratios of the ice itself) have been used to look at the big picture of climate change, most notably the massive glaciations which dominate the climate record of the Earth on time scales of thousands of years. Recently, researchers have been more active in exploiting the high temporal resolution available in ice cores in an attempt to understand and use the information stored in ice cores on time scales of years to decades. While the need for longer records of high resolution climate change is clear, our ability to extract such records from ice cores has not been so clear. Two central problems exist. first, we lack long records of meteorological observations in polar regions, and thus we lack the ability to directly compare proxy records of climate change with locally observed records. Second, the noise in a single high temporal resolution record of stable isotopes in ice cores is often more than 50 percent of the variance, limiting the usefulness of such records. The former problem is endemic to ice cores and can only be attacked indirectly, the latter, however, can be overcome to some degree by taking a lesson from the tree ring community and combining isotope records from many ice cores to produce a record of common variance. This approach has been applied to a suite of seven, annually resolved ice cores from central Greenland. Here, the dominant climate variable recorded in stable isotopes is regional temperature changes and the dominant oscillatory mode in stable isotope ratios is the North Atlantic air pressure oscillation between Iceland and the Azores. The filtered, 7.5 year period of this oscillation compares very well over the past century with modern observations and tree ring records. Prior to this time, however, when modern observations are absent, the tree ring and ice core records of the NAO disagree. Possible explanations for this disagreement are explored.
In coastal west Antarctica, a number of stable isotope records with annual resolution are available as part of the WAIS (West Antarctic Ice Sheet) Project. The dominant climate signature in the cores is strongly related to ENSO, most likely by ENSO affects on the position and strength of the Amundsen Sea Low. Here, the challenge is in dating the cores precisely enough to effectively stack the isotope records and compare the stack with ENSO and tropical SST's. We also compare these ice core records with isotope records from corals in the tropical Pacific.