α‐HCH enantiomer fraction (EF): A novel approach to calculate the ventilation age of water in the Arctic Ocean?

Abstract

α‐HCH (hexachlorocyclohexane) and the enantiomeric fraction (EF) of its mirror‐image isomers have been determined for water column profiles in the southern Beaufort Sea in 2004 and 2007. Using estimated rates of metabolic degradation, we have applied a simple kinetic model to convert the observed EFs to apparent ventilation ages of the water masses in the study region. We found an age of 1.7 ± 0.1 years for the Polar Mixed Layer (PML), 6.6 ± 0.6 for the core of the Pacific Layer centered at salinity 33.1, and 21.7 ± 0.5 years for the core of the Atlantic Layer identified by a Tmax of ∼0.5°C. These ages are in reasonable accord with other methods used to date water masses in the Arctic Ocean suggesting that α‐HCH has an unexploited potential as a dating tool.