Microstructure measurements from the Arcticmix cruise, Beaufort Sea, September 2015

• Main Authors: Jennifer MacKinnon, Matthew Alford, John Mickett
• Format: Dataset
• Language: unknown
• Published: Arctic Data Center 2019
• Subjects: Mixing; Alford; Arctic; Arctic Ocean; Bering Strait; Canada; Pacific; Beaufort Sea; canada basin; Sea ice
• Online Access: https://search.dataone.org/view/urn:uuid:8833c902-030d-4039-b68e-9319ceb3106c

This data is from the NSF funded ArcticMix experiment. The award revolves around better understanding and prediction of the changing Arctic Ocean. Most oceans are `stratified’ by temperature, meaning water density is controlled primarily by temperature. Most oceans have warm water near the surface and cold water at depth, because the cold water is denser and sinks. The Arctic is unusual in that density is set primarily by salinity. The near-surface water is often cold but fresh; the low salt content makes it quite light, despite its low temperature. Below that there are several layers of water that are saltier (and hence denser), but can be significantly warmer than the surface. This unusual layer structure allows the possibility of considerable heat being trapped at depth sub-surface. There are several of these warm layers. In the Beaufort Sea, where this work was performed, there is often a layer of warm water between roughly 30 and 80 meters below the surface that is of Pacific origin; it has entered the Arctic through Bering Strait. Well below that (roughly 250-400 meters down) there is another warm layer coming from the Atlantic. Historically, these sub-surface heat pockets were modest in temperature. They were also fairly fairly stable as they were usually isolated from storms by a cover of sea ice, lurking for years beneath the surface and circulating around basins, only very gradually releasing their heat. In the New Arctic, several things are changing. First, the warmth of the sub-surface layers is increasing. Our focus is primarily on the Pacific origin water, the warmest variety of which is called Pacific Summer Water (PSW). Several decades ago most of this water was of order 1 C. More recent observations (including ours funded by this grant) have seen a new type of PSW arriving which is much, much warmer, up to 6 C. Second, the rate at which this heat is turbulently mixed upwards may be changing, as the Arctic in general becomes more energetic with increasingly ice-free conditions. A better understanding of both the processes that set this sub-surface heat structure and those which may turbulently mix the heat upwards, is crucial for improved forecast abilities for both the sea ice melt rate and a variety of other physical and ecosystem consequences. The data in this file are measurements of the turbulent dissipation rate from a shear-probe equipped microstructure profiler. They were acquired with the "Modular Microstructure Profiler" developed by Mike Gregg at the University of Washington and published using standard techniques. Data format is consistent with that required by the NSF funded microstructure database at https://microstructure.ucsd.edu Results from some analysis of this data (with further information on processing methods) are presented in: Fine, E. C., MacKinnon, J. A., Alford, M. H., & Mickett, J. B. (2018). Microstructure Observations of Turbulent Heat Fluxes in a Warm-Core Canada Basin Eddy. Journal of Physical Oceanography, 48(10), 2397-2418. The instrument also measures standard CTD quantities of temperature, pressure and salinity.