Vostok Ice Core Climate Perspectives

The Nature article “Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica.”  (see https://www.nature.com/articles/20859) provides a wealth of perspectives on climate variations over the last 400,000 years along with some insights into future climate response. The analysis reveals interrelationships between many measurable quantities including CO2, CH4, temperature variations from deuterium (hydrogen atom with a neutron), precipitation rate and more.

The authors illustrate the frequency of variations of measurable quantities (CO2, CH4,...) over the period of observation and their results reveal a persistent 100,000 year (orbital eccentricity) spectral peak. The 41,000 year (axial tilt) peak is often present but of lower amplitude and less consistent.

 

 

The variations associated with eccentricity, obliquity and precession have periods of roughly 100,000 years, 41,000 years and 21,000 years respectively (above). Astronomical forcing with 100,000 and 41,000 year periods is evident for most of the variables, while 21,000 precession seems less persistent. Eccentricity, obliquity and precession orbital features are visually illustrated below (taken from http://deschutes.gso.uri.edu/~rutherfo/milankovitch.html).

 

Petit et al. (1999) (see URL above) note that “temperature and atmospheric concentrations of CO2 and CH4 rise steadily, whereas the dust input decreases. During the last half of the temperature rise, there is a rapid increase in CH4. This event coincides with the start of the d18Oatm decrease.” They also conclude that “Finally, CO2 and CH4 concentrations are stronglycorrelated with Antarctic temperatures; this is because, overall, our results support the idea that greenhouse gases have contributed significantly to the glacial–interglacial change. This correlation, together with the uniquely elevated concentrations of these gases today, is of relevance with respect to the continuing debate on the future of Earth’s climate.” This is an excellent paper to read in detail or skim through as you work through course materials.