Inferring ocean turbulence characteristics from Lagrangian measurements of sea ice acquired via remote sensing imagery
Abstract
Sea ice drift is an important component of the Arctic climate system. In Marginal Ice Zones (MIZ), the dispersion of free-drifting sea ice is hypothesized to be driven by the underlying turbulent eddy field on spatial scales of the order of 10 km. This, in turn, has salient consequences regarding heat and fresh water budgets, and it suggests that the sea ice drift field can act as a proxy for ocean turbulence characteristics in high latitudes. Therefore, understanding the dynamics of sea ice drift fields is fundamental for the study of ocean turbulence in the Arctic. Although much progress has been made on this front through the acquisition of remote sensing observations, characterizing the sea ice drift field and its interactions with the underlying meso/submesoscale eddy turbulence has proven challenging given the range of spatiotemporal scales involved. To alleviate this issue and assure that the Navy can fulfill its mission globally, we propose to retrieve the kinematics of freedrifting sea ice, including daily velocities, rotation angles, and dispersion characteristics from optical remote sensing imagery using a powerful technique that we recently developed. We propose to leverage optical data (often overlooked due to atmospheric stamps and sunlight dependence) to study the evolution of sea ice drift in marginal ice zones (MIZ). To this end, we will process Moderate Resolution Imaging Spectroradiometer (MODIS) imagery unging from 8 to 65 km. As a result, we are able to retrieve sea ice kinematic products that we will use to infer the properties of the meso/submeso-scale (<20 km) eddy field at daily temporal scales. In particular, we will determine the dispersion characteristics of free-drifting sea ice and assess the role of atmospheric and oceanic forcing on ice floe motion. The dynamical regime of the sea ice drift field will be assessed via single- and two-particle dispersion analysis, as these metrics provide a description of the structure of the drift field. By examining the correlation of sea ice drift to external forcing sources, we will assess the influence of ocean turbulence on sea ice motion. Besides studying the topology of the sea ice drift field, we also propose to develop an automatic eddy detection algorithm from MODIS imagery. Our versatile approach to tracking sea ice also allows for the measurement of the rotation of free-drifting ice floes, which provides an additional resource to characterize the turbulent eddy field by quantifying eddy characteristics and their kinematics. With our technique, we will automatically retrieve the geographical location, length scale, and direction of identified eddies for the first time. Such an automatic detection tool can extend our understanding of the formation and dissipation mechanisms of meso/sub-mesoscale oceanic eddies in MIZ. Finally, we will explore sea icghout the years. MODIS provides an opportunity to analyze sea ice dynamics over the extent of the twenty-first century. We will thus characterize and explore the inter-annual variability of the sea ice drift and the turbulent eddy field of MIZ over the last two decades. ONR funding for this project will allow us to integrate a novel and extensive satellite observation database to analyze sea ice-turbulent ocean interactions. The robustness of our method will allow us to acquire long-term observations in key Arctic regions that will contribute to ONR-funded efforts (e.g., the MURI program) to achieving adequate parametrization and validation of sea ice in discrete models. We expect that the remote sensing products acquired through this project will be widely applicable in current D
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 31, 2020
- Source ID
- N000142012753
Entities
People
- Monica Wihelmus
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents