Temporal Variability in Arctic Zooplankton and Phytoplankton Populations from Moored ADCP and Icycler Profiler Measurements

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An instrumented mooring array across Barrow Strait in the Canadian Arctic Archipelago has provided a 10 year data time series that has been used to determine freshwater and heat transports through this important pathway connecting the Arctic Ocean and the northwest Atlantic Ocean. Measurements indicate that 20% of the total freshwater transport out of the Arctic Ocean passes through this 65 km wide passage, but also demonstrate large seasonal and inter-annual variability in these transports. The timing and duration of a short ice free period in the Strait also varies from year to year, resulting in different water temperature, light and mixing conditions throughout the biological growing season. Here, backscatter data from the acoustic Doppler current profilers (ADCPs) used to provide the transport time series, are analysed to study the behaviour, and temporal variability in the relative biomass of the zooplankton population. ADCP transducer calibrations allow for results from two different years to be compared. Daily profiles of fluorescence collected with a new under-ice moored profiler called Icycler are also presented for the same 2 years. Icycler is an innovative winch system designed to profile the top 50 m once a day, using a sonar to allow a sensor package to come to within 2 m of the ice cover. The yearlong fluorescence records provide a unique look at the nature and timing of phytoplankton activity in the Strait. The backscatter and fluorescence results presented are from 2 years for which the physical environment was notably different. High inter-annual variability in the measured biota are identified. The inter-relationship of the zooplankton and phytoplankton populations and correlations with the physical environment are also explored.