Abstract
We developed and deployed two inertial measurement units on mobile pack ice during a U.S. Navy drifting ice campaign in the Beaufort Sea. The ice camp was more than 1000 km from the nearest open water. The sensors were stationed on thick (>1 m) first- and multi–year ice to record 3-D accelerations at 10 Hz for one week during March 2020. During this time, gale-force winds exceeded 21 m per second for several hours during two separate wind events and reached a maximum of 25 m per second. Our observations show similar sets of wave bands were excited during both wind events. One band was centered on a period of ~14 s. Another band arrived several hours later and was centered on ~3.5-s. We find that the observed wave bands match a model dispersion curve for flexural gravity waves in ~1.2-m ice with a Young’s modulus of 3.5 GPa under compressive stresses of ~0.3 MPa. We further evaluate the bending stress and load cycles of the individual wave bands and their potential role in break-up of sea ice. This work demonstrates how observations of waves in sea ice using these and similar sensors can potentially be a valuable field-based tool for evaluating ice mechanics. In particular, this approach can be used to observe and describe the combined mechanical behavior of consolidated floes relevant for understanding sea ice mechanical processes and model development.
Highlights
Widespread Arctic sea ice decline and reduced ice extent [1,2] are increasing the area of ice-free water in the Arctic Ocean
A clear example of significant wave generation in open water occurred during the record-breaking September 2012 sea ice minimum when strong winds (18 m s–1) forced large (5-m) waves in the central Beaufort Sea that evolved into sea swell [6]
We evaluate the sea ice response based on analysis of the measured vertical accelerations, and assess the agreement between the observational data and the dispersion relation for flexural-gravity waves
Summary
Widespread Arctic sea ice decline and reduced ice extent [1,2] are increasing the area of ice-free water in the Arctic Ocean. We have applied the recent advances in sensor development and the available open-source design to produce our own sensors for deployment on the comparatively thick landfast ice north of Alaska and on mobile pack ice in the Beaufort Sea. The sensors, named Ice Wave Riders (IWRs), are built around the VN100 IMU and include Iridium telemetry and battery power for field deployments for up to 60 days [15]. We present measurements from two IWR sensors deployed opportunistically on drifting Beaufort Sea pack ice at a time when gale-force winds were measured up to 25 m s–1. The results presented here, as far as we know, are the first high-resolution accelerometer measurements of flexural-gravity waves from Arctic pack ice under extreme wind forcing. The Results section presents the processed sensor data and includes the dispersion curve for flexuralgravity waves tuned with values for sea ice thickness, Young’s modulus, and compressive stress.
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