The Integrated Sea Ice Dynamics Experiment (SIDEx)
Abstract
To facilitate planning of an observation campaign building knowledge needed to improve operational prediction of Arctic sea ice. The critical knowledge gaps we identify all relate to how stress propagates through a heterogeneous ice cover. We hypothesize that heterogeneity in ice strength controls stress propagation through natural sea ice, creating stress concentrations that govern ice failure locations. If this is true, a model that is initialized with a realistic ice type and strength parameterization map and forced with known wind and ocean currents could skillfully predict locations of failure at the resolution of the ice map. Ice strength and deformation predictions, therefore, depend on understanding the nature of the stress concentrators embedded in the icepack and their interactions with stress transmission. We target four processes governing strength heterogeneities and interaction of stress with these at increasing scales: A. The generation of flaws in otherwise coherent ice by thermal tensile cracking B. The buildup of dynamic stresses on thermal cracks, leading to mechanical fracture C. The transfer of stress between floes during kinematic interactions (shear, ridging) D. The propagation of stress across a heterogeneous multi-floe ice cover We will observe each of these four target processes and test our hypothesis by conducting field programs that collect a dataset over scales from 1 m to 10 km capturing (1) ice stress, (2)elastic or creep strains, (3) the location and size of thermal and mechanical fractures, (4) larger dynamic strains (e.g. shear), and (5) the morphology of the ice. Field observations will be collected in two smaller efforts and an integrated flagship experiment. The two smaller efforts in year 1 and 2 will (1) target thermal expansion coefficients, stresses, and thermal cracking in isolated landfast ice and (2) test new equipment and techniques for observing stress, strain, and fracture in drifting ice. The 2020-2021 flagship program in the Beaufort Sea will collect integrated stress, strain, and deformation observations targeting fracture initiation, ridging, multifloe stress transfer, and deformation scaling processes in drifting pack ice. Synthesis of this data will be based on an analysis strategy that rigorously combines physical models with observational data to produce continuous state fields (e.g., stress, strain, temperature) from spatially and temporally incomplete observations. Extracting these fields will be carried out as a Bayesian inverse problem, probabilistically combining physical models, prior knowledge of model parameters, and observational data. Continuous stress-strain fields before, during, and after failure events, will be used to test theories of fracture initiation and predictability of stress transmission at floe-floe interaction scales based on observable ice morphology; building knowledge to address practical questions like “Can we select a particular floe that is safer for an ice camp?”
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2019
- Source ID
- N000141912606
Entities
People
- Chandra Kambhamettu
Organizations
- Office of Naval Research
- United States Navy
- University of Delaware