A Zonally-Averaged Stable-Isotope Model Coupled to a Regional Variable-Elevation Stable-Isotope Model

Abstract

A global model is presented that simulates zonal averages of stable isotopes δ(18O), δ(D) and precipitation rates at sea level. The model is empirical and uses as input zonal averages of evaporation, meridional water-vapour flux, air temperature, sea temperature, wind speed, relative humidity, sea-ice cover, and supersaturation in clouds as a function of temperature. The global model provides input to high-latitude regional solutions that are found integrating up assumed vapour trajectories, which need not be at sea level. Model precipitation rates, δ(18O) and δ(D), compare well to measured values on an annual and seasonal basis. The stable-isotope-temperature relation poleward of about 35° latitude as well as the isotope-precipitation relation in the tropics is simulated by the zonal global model. The Queen Elizabeth Islands stable-isotope pattern is given as an example of a regional solution of the model. Zonal moisture contributions for high-elevation sites are found to be different between northern hemisphere (Crête, Greenland) and southern hemisphere (Vostok, East Antarctica) with the southern high-latitude cold oceans making a larger relative contribution.

High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution

“…S2). The elevation correction for the isotope records is more complex, as the correction for vertical land motion and thickness changes of the Innuitian ice sheet is applied at the location where the air moisture that precipitates over the ice cap reaches a fixed maximum elevation of condensation (5,6,10,11) (Fig. S3).…”

“…The atmospheric moisture that precipitates onto the Agassiz ice cap primarily passes through (and partly originates in) Baffin Bay. It subsequently encounters the southeastern shores of Ellesmere Island where it is elevated, and given there are no further inland features capable of forcing the air masses significantly higher, the δ 18 O composition in the ice is predominantly sensitive to altitude changes along this shoreline (5,6,10). Thus, the elevation correction is not determined at the drill site, but rather at the location where the air mass initially encounters a major topographical feature along the eastern coastline of Ellesmere Island.…”

Stable Isotope Records from Mount Logan, Eclipse Ice Cores and Nearby Jellybean Lake. Water Cycle of the North Pacific Over 2000 Years and Over Five Vertical Kilometres: Sudden Shifts and Tropical Connections

“…Although it is also sensitive to water cycle history that bears the moisture to the sites (Fisher, 1991;Fisher et al, 1996), d is an indicator of the source ocean temperature. The geographic distribution of δ( 18 O) and δ(D) has been modeled with the help of GCMs and intermediate complexity models (Fisher, 1990(Fisher, , 1992Kavanaugh and Cuffey, 2003). The latter are used to interpret the results presented here.…”

“…A semi-empirical model has been used in a wide range of polar situations, in simulating δ( 18 O) and δ(D) (Fisher, 1990(Fisher, , 1991(Fisher, , 1992Kavanaugh and Cuffey, 2003). For the modern situation, the model inputs multi-latitude sources and uses measured zonal annual averages of major water cycle variables such as evaporation rate, total meridional flux, precipitable water content, precipitation, sea temperature, wind speed, relative humidity, sea ice front, etc.…”

Space and time variation of δ18O and δD in Antarctic precipitation revisited

“…[4] The use of ICMs to examine precipitation isotopes was pioneered by D. Fisher [Fisher, 1990[Fisher, , 1991[Fisher, , 1992Fisher and Alt, 1985], who connected the geographic variations of d to zonally averaged climate quantities (temperature (T), precipitation (P), and evaporation (E )) and to the partitioning of atmospheric transport between advective (mean flow) and diffusive (turbulent eddy) components (following the study of Eriksson [1965]). Hendricks et al [2000] subsequently created the state-of-the-art ICM by explicitly and consistently linking water vapor transport to both the d and the climate variables.…”