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Salpa thompsoni is an ephemerally abundant pelagic tunicate in the waters of the Southern Ocean that makes significant contributions to carbon flux and nutrient recycling in the region. While S. thompsoni, hereafter referred to as “salps”, was historically described as a polar-temperate species with a latitudinal range of 40 – 60°S, observations of salps in coastal waters of the Western Antarctic Peninsula have become more common in the last 50 years. There is a need to better understand the variability in salp densities and vertical distribution patterns in Antarctic waters to improve predictions of their contribution to the global carbon cycle. We used acoustic data obtained from an echosounder mounted to an autonomous underwater Slocum glider to investigate the anomalously high densities of salps observed in Palmer Deep Canyon, at the Western Antarctic Peninsula, in the austral summer of 2020. Acoustic measurements of salps were made synchronously with temperature and salinity recordings (all made on the glider downcasts), and asynchronously with chlorophyll-a measurements (made on the glider upcasts and matched to salp measurements by profile) across the depth of the water column near Palmer Deep Canyon for 60 days. Using this approach, we collected high-resolution data on the vertical and temporal distributions of salps, their association with key water masses, their diel vertical migration patterns, and their correlation with chlorophyll-a. While salps were recorded throughout the water column, they were most prevalent in Antarctic Surface Water. A peak in vertical distribution was detected from 0 – 50 m regardless of time of day or point in the summer season. We found salps did not undergo diel vertical migration in the early season, but following the breakdown of the remnant Winter Water layer in late January, marginal diel vertical migration was initiated and sustained through to the end of our study. There was a significant, positive correlation between salp densities and chlorophyll-a. To our knowledge, this is the first high resolution assessment of salp spatial (on the vertical) and temporal distributions in the Southern Ocean as well as the first to use glider-borne acoustics to assess salps in situ.

Remote regions across Alaska are challenging environments for obtaining real-time, operational observations due to lack of power, easy road access, and robust communications. The Alaska Ocean Observing System partners with government agencies, universities, tribes and industry to evaluate innovative observing technologies, infrastructure and applications that address these challenges. These approaches support acquisition of ocean observing data necessary for forecasting and reporting conditions for safe navigation and response to emergencies and coastal hazards. Three applications are now delivering real-time surface current, sea ice, and water level data in areas not possible a mere 10 years ago. One particular challenge in Alaska is providing robust alternative power solutions for shore-based observing. Remote power options have been evolving alongside resilient technologies and are being designed for freeze-up conditions, making it possible to keep remotely deployed operational systems running and easy to maintain year-round. In this paper, three remote observing approaches are reviewed, including use of off-grid power to operate high-frequency (HF) radars for measuring surface currents, a real-time ice detection buoy that remains deployed throughout the freeze-up cycle, and a high-quality water level observing alternative to NOAA’s National Water Level Observing Network (NWLON) installations. These efforts are highly collaborative and require working partnerships and combined funding from other interested groups to make them a reality. Though they respond to Alaska’s needs including Arctic observing, these approaches also have broader applications to other remote coastal regions.