Monitoring Arctic Sea Ice in the Beaufort Sea
Customer: NOAA PMEL
Over the past five years, the loss of sea ice in the Arctic has been dramatic, resulting in an unprecedented warming of the upper ocean during the summer and early autumn months. Satellite data indicate that the summertime ice-free area in the Beaufort Sea has increased roughly 80 percent since 2007.
The impact of this warming of the ocean and the atmosphere is not well understood and has been limited by the ability to observe the surface layer of the seasonal ice zone – a technically and operationally challenging domain – in a sustained and economical manner.
Two Arctic Wave Gliders covered over 900 nautical miles (1,325 and 1,418 respectively) and recorded and transmitted nearly 900,000 temperature measurements, forming a data set that shows the Beaufort Sea was anomalously warm in the summer of 2011.
How We Helped
To overcome these issues, NOAA Pacific Marine Environmental Laboratory (PMEL) deployed two Liquid Robotics Wave Glider® autonomous marine robots for extended research missions in the challenging Beaufort Sea. The mission objectives were to collect critical temperature data in the upper 6 meters, with one Arctic Wave Glider (AWG) leading the other by 12 hours to study diurnal heating effects and to take surface images from an aft-mounted camera for situational awareness near the ice edge to aid navigation and route planning. Another major goal was to evaluate the Wave Gliders’ power generation and management at high latitudes.
A 900-nautical-mile track line loop was laid out, based on scientific need, ocean currents and the best available information of ice location from late July 2011 to the recovery date in mid-September 2011. Both Wave Gliders exceeded the goal of 900 nautical miles (at 1,325 and 1,418 nautical miles) and recorded and transmitted nearly 900,000 temperature measurements, forming a data set that shows the Beaufort Sea was anomalously warm in the summer of 2011.
Six RST Instruments Ltd. (Maple Ridge, Canada) ThermArray thermistors were molded into the tether connecting the Wave Glider's float and sub, at depths of 0.5, 1, 1.5, 3, 4.5 and 6 meters, in addition to a standard satellite-based command and control, and data-handling package. Communication was through an RS-485 transceiver to the command and control electronics. Measurements were recorded on board the AWG and transmitted in near real time at user-selectable intervals. A one-minute interval was chosen for this mission, which was oversampled but allowed researchers to evaluate sending large files through the Wave Glider platform.
Over the course of the mission, continuous in-situ temperature observations from the AWGs were consistent with occasional satellite-derived SSTs from MODIS. The AWGs demonstrated that high-quality temperature measurements from the upper ocean can be collected by robotic platforms in a harsh environment and telemetered in real time. While surface temperature can be observed by satellites, these measurements are infrequently available because of cloud cover, and they yield no information about the total heat storage in the wind-mixed layer. Autonomous systems such as the Wave Glider can fill this observation gap. The AWGs averaged about 1 knot over 54 days and survived anomalous currents and ice, and solar power was effectively collected and managed through late September in a region with extremely high cloud cover.