Helicopter-Based Ocean Observations Capture Broad Ocean Heat Intrusions Toward the Totten Ice Shelf

The recent discovery of warm ocean water near the Totten Ice Shelf (TIS) has increased attention to the Sabrina Coast in East Antarctica. We report the result of 6-day helicopter-based observations conducted during the 61st Japanese Antarctic Research Expedition (JARE61), revealing warm ocean water (0.5-1 & DEG;C) occupying a large previously unsampled area of the Sabrina Coast (116.5 & DEG;E-120 & DEG;E) below 550-600 m. Along the TIS front, we observe modified Circumpolar Deep Water (mCDW) well above freezing (& SIM;-0.7 & DEG;C), consistent with previous work. We identify glacial meltwater outflow from the TIS cavity west of 116 & DEG;E. No signs of mCDW intrusions toward the Moscow University Ice Shelf cavity are observed; however, those observations were limited to only two shallow (& SIM;330 m) profiles. We also highlight the advantages of helicopter-based observations for accessibility, speed, maneuverability, and cost-efficiency. The combination of ship- and helicopter-based observations using the JARE61 approach will increase the potential of future polar oceanographic observations. Totten Glacier hosts the most rapidly thinning ice in East Antarctica. This record of thinning is due to rapid melt along the grounding line of the Totten Ice Shelf (TIS), where warm ocean water from the open ocean flows into ice shelf cavities. To understand the pathways and mechanisms of warm water inflow, ocean observations for entire continental shelf regions are necessary. This has historically not been possible due to intense sea ice and icebergs in the region. To overcome this problem, we conducted a 6-day helicopter-based oceanographic campaign during the 61st Japanese Antarctic Research Expedition. Our measurements show that warm ocean water occupies a large area of the continental shelf off the TIS. We identify glacial meltwater outflow from the TIS cavity west of 116 & DEG;E, which provides direct evidence of TIS melting. We also show that helicopter-based measurements are better for the following aspects; (a) helicopter operations are insensitive to sea ice conditions, (b) helicopter travels faster than a ship, (c) helicopter can conduct measurement in a small ice crack, and (d) helicopter is cheaper to operate than an ice breaker. By combining ship-based and helicopter-based approaches, we may be able to enhance the efficiency of future polar oceanographic observations. Six-day helicopter-based observations retrieved 67 temperature profiles covering the entire continental shelf region off the Totten Ice Shelf (TIS)Between 116.5 & DEG;E and 120 & DEG;E, modified Circumpolar Deep Water can be found uniformly over the continental shelf region below 550-600 mGlacial meltwater outflow from the TIS cavity is identified west of 116 & DEG;E