Using Ice-Tethered Profilers to Examine Production in Sub-Ice Ecosystems


Arctic Research Initiative/OCCI Funded Project: 2008


Arctic sea ice in summer 2007 reached a record minimum in the Canada Basin. Loss of sea ice area is accompanied by decreases in the thickness of the remaining ice, with an effect that photosynthetic organisms living at and below the ice-ocean interface receive more light. These increased light levels will most likely lead to considerable alterations in photosynthesis, primary production, food webs, and biogeochemical cycles in these ecosystems. However, even dramatic changes in ice-covered ocean ecosystems will remain effectively hidden from view because these environments are not easily sampled.  Ice-Tethered Profilers (ITPs) have proven to be a robust approach for measuring ocean physical properties in permanently ice-covered regions. Two ITPs deployed in the Canada Basin demonstrate the ability to reliably measure dissolved oxygen (DO) in addition to standard physical properties over long time scales. The two DO time series collected with these ITPs exhibit seasonal trends that reflect spring-summer bursts in ice algal and phytoplankton production. These time series also bracket the dramatic 2007 reduction in summer sea ice. The goal of this proposed research is to develop a first order model of the physical and biological processes that control DO concentrations in the surface ocean under permanent Arctic ice. This model will be used to determine which aspects of DO variability in ITP data reflect changes in ice properties such as thinning, which reflect ocean physics and chemistry, and which represent the residual variability that should be ascribed to photosynthesis by ice algae and phytoplankton.  Developing this conceptual model and evaluating it against ITP DO measurements will require a strong synthesis of physical and biological expertise. To our knowledge, this interdisciplinary effort will represent the first use of data from autonomous ice-based observatories to assess temporal changes in an Arctic ecological process.