Toward an Understanding of Global Change Initial Priorities for U.S. Contributions to the International Geosphere - Biosphere Program (1988) / Chapter Skim
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Earth System History and Modeling
Earth System History and Modeling
Pages 201-214
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From page 201... ...
In the context of understanding and predicting global change the continued development of a variety of earth system and subsystem models is clearly needed in light of the underlying complexity. Model development generally places great demands on available contemporary data, and unfortunately, little independent information about the present is available for mode!
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From page 202... ...
Paleoclimatic and paleohydrological research reveals numerous climatic events and trends that characterize the past few million years. These include histories of glacier extent, global ice volume, surface ocean temperature, abundances of CO2, CH4, and other trace gases in the atmosphere, extent of forests and arid zones, and sea and lake levels.
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From page 203... ...
Additionally, higher temporal resolution ice core records from high latitudes and carefully selected high elevation ice caps in both middle and Tow latitudes offer critically important shorter records with fine temporal detail. The marine sediment record reveals that the warm global climates that characterized the past 10,000 years are but the interglacial phase of an ongoing glacial-interglacial cycle.
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From page 204... ...
that grew in shallow water or may be obtained indirectly by examination of the organic or inorganic content of age-dated cores taken from lake basins. Groundwater recharge events can also be age-dated and the carbon and oxygen stable isotope ratios used to infer change in temperature or moisture source region.
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From page 205... ...
Another related synthetic role of models is to optimally assimilate observations of complex fields of related variables, as is now done in global weather prediction systems. Such assimilation constrains the observations through known physical laws and uses these physical laws to extrapolate and interpolate from the observations to data-poor locations.
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From page 206... ...
Major physical oceanographic programs such as The World Ocean Circulation Experiment and complementary biogeochemical programs such as Joint Global Ocean Flux Study set the stage for rapid advances in ocean biogeochemical modeling. But in all of these areas, we are faced with extremely difficult problems of methodology and data availability, as wed as a multiplicity of feedbacks at varying spatial and temporal scales that connect the physical-climate system to the biogeochemical system.
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From page 207... ...
The modeling and data analysis efforts could be usefully focused on two key temporal periods: the past 25,000 years and the most recent 1,000 years. In both cases, special consideration could be given to periods of rapid change since large abrupt changes in the global system (Younger Dryas, Little Ice Age, major episodes of volcanic activity, and El Nino events)
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From page 208... ...
Postglacial conditions have been mapped by the Cooperative Holocene Mapping Project (COHMAP Members, 1988~. One suggested modeling thrust toward interpreting the paleorecord over the past 25,000 years is the application of mesoscaTe models coupled to global models.
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From page 209... ...
This intensive study of the naturally archived records of the past 1000 years should inclu(le comparisons with available "ground truth" data contained in direct historical accounts such as weather and sea records. While this sort of comparison is routinely done in the course of sharply focused studies of specific environmental parameters—as in calibrating tree ring widths in a given location in terms of soil moisture or other meteorological parameters such a study has never been organized for multiple parameters focused on an extended test period.
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From page 210... ...
; tree ring data, including ring width and hydrogen, oxygen, and carbon isotope ratios (annual resolution with the potential of discriminating spring/summer seasons in early and late wood) ; high-resolution terrestrial sediment sequences (pollen, runnoff at decadal resolution)
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From page 211... ...
Fine-scale sampling of peats and laminated lake sediments provides detailed studies of vegetation change. High priority should be given to studies of vegetation dynamics during periods when independent data from ice cores record rapid changes in the environment.
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From page 212... ...
Specifically, models of global biogeochemical cycling that consider nutrient interactions and of the hydrologic cycle in specific geographic regions need to be developed. Moreover, efforts need to focus on linking global models of the biogeochemical system to global climate models.
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From page 213... ...
1987. Evidence of abrupt climatic change during the last 1,5Q0 years recorded in ice cores from the tropical Quelccaya ice cap, Peru.
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