The Deep Arctic Ocean as an Indicator of Climatic Shifts
OCCI Funded Project: 2006
Proposed ResearchRecent studies have shown that the deep waters of the Canada Basin in the Arctic Ocean have been in isolation from shallower waters for at least the past 500 years. This prompts the following questions of key climatic importance: Did a climate shift in the recent past prompt an end to new influxes to the deep Canada Basin? If so, how? The dense Canada Basin deep water most likely originated when salty brine was expelled by ice formation at the surface. In the present climate, adequate volumes of surface water sufficiently dense to reach the deep waters are not generated by ice formation. In a different climate regime, however, in which there is less permanent ice cover, the capacity for extensive new ice growth could re-start deep water renewal. This would likely have a strong feedback effect involving the surface and shallower waters. I propose to investigate, both analytically and numerically, the fundamental relationships between ice growth and deep-water renewal. The aim of this proposed research is to explicitly understand how the present day properties of the Arctic deep water can give insight into past Arctic climate patterns and recent climate transitions. Furthermore, the proposed research will assist in understanding how future changes in the Arctic deep water may signal an Arctic climate in transition.
Progress ReportMy research thus far has been an investigation of the relationships between ice growth and deep-water renewal with the aim of understanding how the present-day properties of the Arctic deep water can provide insights into past Arctic climate patterns and recent climate transitions. I have quantified the penetration depth of dense flows produced by ice formation, where the forcing from ice growth is specified by both contemporary and hypothetical ice cover scenarios. I have calculated the conditions necessary for surface water to become sufficiently dense to sink into the deep basin. My future research will involve relating this to ice cover and climate in the Arctic.
I have begun collaboration with Marika Holland at the NationalCenter for Atmospheric Research (NCAR) on a numerical climate modeling aspect of this research. Our goal is to identify changes to the deep water caused by reducing the summer sea ice to an extent that is characteristic of global warming scenarios. The numerical model investigations will provide a basis for understanding to what extent deep-water renewal events can be used as indicators of a shifting Arctic climate, and aid in the interpretation of field observations. If future observations in the deep CanadaBasin indicate new salty influxes, what can we infer then about the shifting climate state?