Investigation of Upper Ocean Submesoscale Dynamics in the Nordic Seas using Glider-based ADCP and Microstructure Observations
Abstract
Arctic and Atlantic waters meet and undergo significant mixing and transformation in the Nordic Seas. Wind forcing and air-sea excha nge of buoyancy fluxes drive the variabilities in upper ocean stratification and mixed-layer depth, with large heat loss in the wint er that can lead to convective overturning of the upper water column. The Arctic Front in the central Nordic Seas supports the north ward flowing Norwegian Atlantic Front Current, which has much stronger flow velocity in winter than summer. Strong atmospheric and o ceanic gradients in temperature, salinity, and velocity lead to frontal instability and strong mesoscale and submesoscale eddy forma tion. In this observational study we focus on a region of strong thermohaline gradients and eddy activity at the interface between t he Norwegian and Lofoten Basins. We aim to directly measure upper ocean flow and turbulence fields using an Alseamar SeaExplorer X2 glider simultaneously equipped with ADCP and turbulence microstructure sensors. This novel suite of sensors has not been previously deployed on a glider platform in the Arctic or the sub-Arctic. Leveraging technology acquisition supported by U.S. IOOS and MARACOOS , our team will apply this new integrated glider system for naval oceanographic research in the ice-free Nordic Seas. The direct mea surement ofhydrography, flow, and turbulence will provide novel insight into the dynamics and energetics of mesoscale and submesosca le processes in the region. The specific goals of the proposed project are: (1) to better understand how seasonal cooling and energe tic storm events drive upper ocean turbulence in both wind-dominated and/or the convective conditions, (2) to gain direct observatio nal insight into how energy cascades from the submesoscale down to the dissipation scale in density compensated frontal region with strong eddy activity, and (3) to observe the effect of flow-eddy-topography interactions along the Arctic Front under different forc ing conditions. Between summer 2022 and summer 2024, we plan to deploy our SeaExplorer X2 glider during the seasonally stratified a nd the convectively mixed winter seasons to capture the submesoscale flow and turbulence fields in a frontal region due east of Jan Mayen. The glider will fly both across andalong the Arctic Front to capture submesoscale processes under different oceanographic con ditions. Each deployment will last approximately 30 days which is sufficient for 3 to 6 transects of 100 to 200 km (deployment can b e extended to 50 days when using lithium primary batteries instead of lithium rechargeable batteries). Collectively, we aim to sampl e during both quiescent conditions as well as energetic events with strong air-sea interactions and capture the rapid evolution of u pper ocean frontal and density structures. Direct comparison between glider observations and ocean models will help identify regions of significant modeling error in terms of ocean state estimate and energy dissipation. The findings of this study will help to impr ove mesoscale and submesoscale forecast, as well as subgrid scale parameterization of submesoscaleprocesses in future high-resolutio n operational ocean and acoustic models.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2021
- Source ID
- N000142112701
Entities
People
- Donglai Gong
Organizations
- Office of Naval Research
- United States Navy
- Virginia Institute of Marine Science