Shigeru Aoki1, Takeshi Tamura2 and Team ROBOTICA
1 Institute of Low Temperature Science, Hokkaido University
2 National Institute of Polar Research
ROBOTICA Figure 1
The importance of sustained observations to describe the variabilities and changes of the ocean and ice around Antarctica - even at an interval of two to three decades - was stressed as early as the IGY period. Starting in 1976, occasional year-round hydrographic observations under the fast ice have been conducted in Lützow-holm Bay by Japanese wintering parties. This data provides one of the oldest annual observational records. Together with the asset of long records from the tide gauge at Syowa station, Lützow-holm Bay provides an important monitoring site for the description of oceanic temporal variability. However, a constant and sustained observation system has not yet been established due to the logistic difficulties of working with sea ice. Hydrographic observations in the neighboring regions have also been limited, largely due to difficulties in ship operation. Even the bathymetric information, which is essential in any discipline of oceanography including navigation, is still insufficient in this sector of the Antarctic Coast. However, recent rapid progress in the techniques of remote autonomous observation and satellite communication has begun to change the game. This is where the project called ROBOTICA comes in: for the coming 9th six-year plan (2016-2023) of the Japanese Antarctic Research Expedition (JARE <http://www.nipr.ac.jp/english/antarctic/index.html>), we plan to implement broad under-ice oceanographic, geographical, and cryospheric surveys using ROV/UAVs, sustained oceanographic observations using tethered and moored profiling platforms, and an ice-surface network of ice/ocean motion and deformation using GPS/ GNSS (See Fig. 1).
The unique characteristics of interactions among climate subsystems in East Antarctica have recently been revealed, and evidence of variations on various time scales - from decades to millennia - have been accumulating. Beneath the Totten Glacier Ice Shelf (located just off Wilkes Land), ice discharge is accelerating, and a new potential pathway of warm water access has been discovered. Geological evidence has been discovered that points to the substantial disintegration of ice sheets on George V Land during the Pliocene, when the surface temperature was higher by several degrees than that of the present climate. At the same time, coastal polynyas are ubiquitous along the East Antarctic coast. Sea ice formation and subsequent brine rejection in polynyas, including Cape Darnley and Vinceness Bay Polynyas, result in the production of Dense Shelf Water and lead to the export of bottom water. Changes in the icescape, such as a Glacier Tongue calving, have a significant impact on oceanic conditions, changes in sea ice production, and the subsequent formation of Dense Shelf Water. The environment is quite different in the neighborhood of the Lützow-holm Bay off Enderby Land, where Japan has maintained a year-round station ever since the IGY era. Coastal polynyas are rare here, but fast ice develops and the icescape varies from year to year. A trace of oceanic temperature variability on decadal time scale has been observed, and disintegration/stabilization of the landfast ice and Shirase Glacier Tongue have a quasi-periodicity of one to two decades (Fig. 2). ROBOTICA is initiated to understand the wide range of ice-ocean interactions and long-term variabilities off the East Antarctic Coast.
Combining such new technologies with conventional and robust observational techniques will enable us to acquire more detailed environmental information, both in time and space. Implementation of this project in the region off Enderby Land represents a big step forward towards the realization of the dream of a sustained observation system around Antarctica. Applying these remote observation techniques to insufficiently explored regions – such as those off the Totten Glacier and Cape Darnley - will enhance our understanding of the mechanisms of different ice-ocean interaction regimes. In cooperation with the international research community, ROBOTICA will contribute to the development of the future observational network.
Observation plan and data will be provided here: <http://www.lowtem.hokudai.ac.jp/en/groups/acros.html>