Is the Isotope Composition of Snow a Reliable Temperature Indicator?

[Andre]

In several threads I have tried to discus the ice cores of Greenland and Antarctica about not being accurate paleo-termometers and those glacial interglacial spikes were hardly about big temperature changes but told much more about changes in precipitation patterns (caused by some pet idea).

I may have shown graphs like http://home.wanadoo.nl/bijkerk/vostok-cor2.GIF showing the extreme tight correlation between (relative) annual ice layer height and isotopes.

Of course the thermometer is the isotope composition of the precipitation which means that you can only measure temperature when it snows (or rains), a temperature, which may be far off the real average temperature especially with changing seasonalilty of precipitation. So those big spikes in the 100,000 years that show a tight correlation with precipitation may have a different message than temperature.

The beauty of being right is, that sooner or later some study will confirm it:

pp 38:

AWS data revealed that during accumulation, temperature is above average. This effect is most pronounced in winter and at low-accumulation sites such as the Antarctic plateau.

From the summary: pp 143-145

The interpretation of stable isotopes in Antarctic snow is the subject of this thesis. Isotope ratios of oxygen (d18O) and /or deuterium (dD) are widely used as proxies for atmospheric temperature, on a variety of time scales. A significant spatial correlation between mean annual surface temperature (Ts) and the average isotopic composition of snow (d) is commonly used as argument to use d values a a paleothermometer. However, previous research has shown that this spatial d - Ts relation is also influenced by other processes, and is not always constant over time. This obscures the interpretation of isotope records, and points out that isotope records from ice cores should not be quantitatively translated to temperature changes without calibration, using independent temperature records.

 

[Mk]

How do you pronounce d180 and dD?