In Situ Observations of the Thermal Strain Coefficient of Sea Ice

Abstract We conduct observations of sea ice thermal strain using a laser theodolite in situ (0.3–1 km distances) and InSAR remote sensing (1–22 km). We capture the thermal strain relationship of sea ice at geophysical scales never before measured. Net strain was, unexpectedly, observable only in cooling First Year Ice below −11°C and found to be dependent on cumulative, as opposed to net, temperature decrease. Prior work, at smaller scales, shows other behaviors. Analysis in the context of prior work and theory indicates multiple processes driving sea ice thermal strain. Strain is a combination of (a) solid ice matrix expansion/contraction, (b) expansion/contraction due to brine inclusion phase changes, (c) apparent mass exchange of brine from non‐enclaved inclusions, (d) apparent internal void formation, and (e) internal stress state. We hypothesize that differential thermal strain in First Year and Multi‐Year Ice contributes to changing ice strength and deformation rates observed in the Arctic.