NOAA/WDS Paleoclimatology - Global Lake-Level Variations from 18,000 to 0 Years Ago: A Paleoclimatic Analysis

STUDY NOTES: Lake status determined at 1000-year intervals between 30 ka BP and the present day (0 ka BP = 1950 AD). The sampling scheme used in this report has the effect of suppressing shorter-term variations, which tend to reflect regional climatic and hydrological perturbations, and emphasizing longer-term global variations. A standardization procedure was applied in order to render all basins comparable, regardless of size. The total range of fluctuation experienced by each basin during the past 30,000 years was divided into three lake-status categories with a similar overall frequency of occurrence in the data set (Street and Grove, 1976,1979): LOW 0-15% of the total altitudinal range of fluctuation, including dry lakes INTERMEDIATE 15-70% of the total range HIGH 70-100% of the total range of fluctuation, including overflowing lakes. For basins where the absolute range of lake levels could not be determined, the relative lake level was coded in the following way: when the lake was at or near its deepest or freshest, it was coded as HIGH and when at or near its lowest or most saline, as LOW. Periods for which there was unambiguous evidence that the lake fell between these states were assigned to the INTERMEDIATE class. For many of the basins in the data bank, a continuous record of water level has been published or made available to us. In such cases, it was possible to determine the trend in water level at 1000-year intervals as RISING, STABLE or FALLING. If no trend information was available for a particular time period, trend was classified as UNCODABLE. The Oxford Lake-Level Data Bank comprises records of lake status, a measure of relative water depth, for lake basins which have been closed for part, or all, of their Late Quaternary history. The data base is arranged regionally in the following order: (1) Africa; (2) South and Southwest Asia (including Afghanistan and India); (3) China; (4) Soviet Union; (5) North America (U.S.A. and Canada, in that order); (6) Mexico; (7) South and Central America; (8) Australasia (Australia, New Zealand and Papua New Guinea, in that order); (9) Europe and Greenland. Within each regional block the order of the basins is alphabetical. For North America, basins are listed alphabetically by state or province. The full data bank is stored in two NOAA template files: one contains the radiocarbon dates used to determine lake status (oxford_lldb_14C-noaa.txt), and the other contains the lake status and trend information (oxford_lldb_levels-noaa.txt). Original, non-templated files that were contributed to the World Data Service for Paleoclimatology are also available from the NOAA Landing Page. Refer to original Appendices C, D, and E for additional lake metadata, publication index numbers by lake, and full citation information for each publication index, respectively.
ABSTRACT SUPPLIED BY ORIGINATOR: Fluctuations in the water levels of lakes are an important source of information about past climates, and can be used to validate paleoclimatic simulations made with atmospheric general-circulation models. The Oxford Lake-Level Data bank contains information about variations in the water levels of approximately 360 lake basins during the last 30,000 years. This data set was compiled as part of COHMAP (the Climates of the Holocene Mapping Project). In this report, regional and global maps of lake status (coded as high, intermediate or low) at 18, 15, 12, 9, 6, 3, and 0 thousand years before Present are presented and compared with numerical simulations for the same time slices carried out with NCAR Community Climate Model. Although agreement between the data and the model is generally excellent, significant discrepancies occur. These may reflect the effects of changes in boundary conditions that were not included in the experiments, for example increases glacial-age aerosol loadings, as well as the inability of the model to portray some of the complexities of the climate system such as oceanic circulation and orographic effects.