For example, in the Greenland ice core (GISP2), sea salts (sodium (Na)) concentrations strongly correlate to regional wind strengths (the westerlies) and to semi-permanent pressure centers (the Icelandic Low and the Siberian High).
The correlations reflect that the strengthening of regional wind speeds and the Siberian High and deepening of the Iceland low lead to enhanced entrainment and transport of sea salts and dust; meaning higher concentrations in the ice core.
Seasonal markers such as stable isotope ratios of water vary depending on temperature and can reveal warmer and colder periods of the year.
Other seasonal markers may include dust; certain regions have seasonal dust storms and therefore can be used to count individual years.
Analysis of the physical and chemical properties of an ice core can reveal past variations in climate ranging from seasons to hundreds of thousands of years.
We know that it is older than Christendom, but whether by a couple of years or a couple of centuries, or even by more than a millenium, we can do no more than guess." [Rasmus Nyerup, (Danish antiquarian), 1802 (in Trigger, 19)].
Nyerup's words illustrate poignantly the critical power and importance of dating; to order time.
The Holocene is the current interglacial and it has persisted for the last ~11 thousand years.
Comparison between ice core temperature reconstructions and ice core trends are consistent with the nature of greenhouse gases (GHGs); the higher the concentration of GHGs in the atmosphere the greater the amount of heat that can be “trapped” in the atmosphere.