Autonomous CTD Profiling at the Edge of Calving Glaciers
Arctic Research Initiative
2013 Funded Project
SummaryGreenland lost four times as much ice in 2000-2011 than it did in 1992-2000 [Shepherd et al.2012]. Recent mass loss amounts to one and half times the weight of Mt. Everest (i.e. about 580 trillion pounds) every year. This ice ends up in the ocean and, between 1992 and 2011, Greenland caused a rise in global sea level of a 1/3” [Shepherd et al. 2012]. This dramatic loss was unexpected and unpredicted by models. It has been largely associated with the speedup and thinning of marine-terminating glaciers in southeast and western Greenland [Rignot et al. 2006; Stearns and Hamilton 2007] and was likely triggered by ocean warming [Straneo et al. 2013; Joughin et al. 2012]. The glacier/ocean link represents a new, previously overlooked, wiring of our climate system. Understanding the relevant mechanisms and including them in the models is crucial to sea level rise predictions over the next decades [IPCC, 2007]. To do this, we need measurements from the glacier/ocean interface – where the ocean-driven melting occurs and where the key processes that are absent from the models can be observed.
Making measurements at the edge of Greenland’s glaciers, however, is easier said than done. The region adjacent to the large glaciers is choked with ice of all sizes (from mile-long, half a mile-deep icebergs to sea-ice bits) and even icebreaking vessels have to turn around tens of miles from the glaciers. Even small glaciers pose a major challenge since, even though the glacier can, in principle, be reached with a smaller vessel, the continuous breaking off of ice makes the near-glacier region highly dangerous. To circumvent this problem, scientists Straneo, Das, Plueddeman and Singh conducted a pilot experiment using an autonomous underwater vehicle (the REMUS 100) at the edge of a relatively small glacier in West Greenland. The project, funded by the Arctic Research Initiative through WHOI’s Ocean and Climate Change Institute (OCCI), was highly successful. We collected unique data and demonstrated that driving underwater vehicles near glaciers is feasible. Our field experiment, however, also highlighted the weaknesses of using an underwater vehicle. These vehicles are expensive and the risk of vehicle loss makes it impractical to drive it within several hundred feet of the glacier. Furthermore, communications with the vehicle requires a cumbersome infrastructure of underwater buoys and even then is sometimes problematic.
Building on this experience, we propose to make near glacier measurements using a surface autonomous vehicle – a jet powered kayak (the ‘Jetyak’) – which has been recently developed and tested by WHOI engineers and scientists. The Jetyak is a light, inexpensive option which can carry a full suite of oceanographic instruments and can be remotely operated using in air communications. Here, we request some funds to outfit the Jetyak with a winched CTD (conductivity, temperature, depth recorder) to collect unprecedented data from the edge of the glacier. This work brings together an interdisciplinary team of WHOI scientists and engineers and has the potential to revolutionize our understanding of glacier/ocean interactions. It leverages funded fieldwork and will provide data for a new OCCI post-doc who will be participating in the fieldwork.
One of the leading hypotheses to explain the glacier speed up and retreat is that glaciers are responding to a warming of the ocean waters near their margins. Glacier/ocean interactions, however, are not well understood. They involve scales from the molecular to the large scale ocean gyres and are intrinsically difficult to measure because of the inaccessibility and dangers of making measurements at the margins of Greenland’s calving glaciers. Also, they involve multiple disciplines (glaciology, oceanography, climate, sea-ice, atmosphere) which need to come together to address this important question. A recent study released in August in the Bulletin of the American Meteorological Society lead by WHOI scientist Fiamma Straneo, and co-authored by 15 leading scientists, summarizes what we know about glacier/ocean interactions in Greenland and identifies a series of steps on how to move forward on this important problem.