Project 4096

Ice shelves are a key component of the ice-ocean climate system and are vulnerable to projected changes in ocean temperature. They play a pivotal role in the discharge of ice to the ocean and its contribution to changes in sea-level. This project will conduct a comprehensive study into the current state of the Amery Ice Shelf system, combining surface glaciological measurements with sub ice oceanography in a detailed analysis of ice shelf stability and its response to changes in the ocean.

Significant progress has been made with the processing and interpretation of our oceanographic data collected as part of the AMISOR project (AAS 1164) and the calibration of the DTS data.
The project was also able to visit two of the 6 Amery Ice Shelf field sites during the 2012/13 field season. During the visit the field team was able to download data from our sub ice moorings (CTD data) and from the two fibre optic based temperature loggers (Distributed Temperature Sensing – DTS). AM06 produced a full winter season of temperature data, while the DTS system at AM05 failed in the early part of 2012 (April) and was sent home for repair. As part of servicing the AM06 Station a new tower structure with additional solar and wind power was erected and a GPS instrument and a seismometer were installed. The tight field schedule did not permit to investigate in greater detail the fault of the sub-ice ocean current meter (ADCP) at AM06 and or the servicing of the power system at AM05.

The processing and interpretation of oceanographic data collected as part of the predecessor AMISOR project (AAS 1164) continued with four accepted peer-reviewed publications, including: research on seasonal variability of ice/ocean interactions and implications for marine ice formation, and on indirect inference of marine ice accretion processes and rates from abrupt variations in pressure measurements. Unfortunately intended acquisition of new oceanographic data was not possible as we were unable to visit Amery Ice Shelf field sites this season as air operations at Davis Station (Antarctica) were suspended after a helicopter crash. Download of our CTD and DTS data, instrument installation and servicing of our two ground stations is thus postponed until the beginning of the 2014/15 field season.

This summer it was possible to visit the Amery Ice Shelf, download data and service equipment at AM06. We were also able to install a phase sensitive radar for an add-on project funded through the Antarctic Gateway project. Unfortunately all but 1 of our microcat CTD's had run out of battery power. New Distributed Temperature Sensing (DTS), GPS and seismic data was acquired for parts of 2013, while due to a power system failure no data was collected during the 2014 winter. Due to time limitations only equipment at AM06 could be maintained for data acquisitions during the 2015 winter. All 2014/15 field season data has been submitted to the AAD Data Centre and some minor issues with older data have been corrected. The processing and interpretation of Amery Ice Shelf data continued with two accepted peer reviewed publications.

Activities on the Amery Ice Shelf during 2015/16 field season were curtailed due to unfortunate incidences at both Davis and Mawson stations, and the injury of a field staff member during a late season site visit. Data was recovered at site AM06 from the ApRES units and the DTS. Unfortunately, the automatic logging of the last remaining CTD did not occur with no additional CTD data recovered this season. No DTS measurements were made at site AM05, and remain to be done. As next season is the last year, a request will be made that the project is extended by one year so as to complete coincident DTS measurements at both sites AM05 and AM06. Initial reports on the DTS progress are planned to be reported on at an international meeting in June with several papers published and under review. The last year has also seen the completion of one student and the start of another.

Activities on the Amery Ice Shelf during 2016/17 field season were again not completed due to being unable to have enough time in the field. Data was recovered at site AM06 from the ApRES units and the DTS. Again, no DTS measurements were made at site AM05, and remain to be done. As next season is the last year, a request will be made that the project is extended by one year so as to complete coincident DTS measurements at both sites AM05 and AM06.

The primary focus of AAS4096 was the development of new insights into fine scale oceanic processes driving melting and freezing beneath the ice shelf. The project ran over a period of seven years from 2012/13 until 2018/19. The project analysed a combination of new data from instruments installed over the project, legacy data from previous projects, the development of new theory and numerical modelling. The new data collected from instruments were installed at the surface at boreholes drilled in previous seasons as part of the AMISOR experiment (AAS 1164). Sites selected for intensive study in this project are where the ocean was thought to be primarily driving relatively high rates of melting (AM06) and refreezing (AM05). New data was collected from Distributed Temperature Sensing (DTS), GPS, Autonomous phase-sensitive Radio Echo Sounding (ApRES) instruments. Extensive progress was made on the analysis of legacy data and with numerical modelling that resulted in several papers published on these aspects. The analysis of ocean measurements from site AM06 has shown present methods for calculating the rates of sub-ice-shelf ocean melting cannot reproduce the observed ice-shelf basal melt rates. These measurements show very different results to the only other measurements made of this type from the Ronne-Filchner Ice Shelf, with implications for how ice-shelf basal melt rates are calculated in numerical models. The incorporation of these results into future climate projects will be important to be able to understand the future evolution of ice shelf melting and rate of global sea level rise that can occur as more of the ice sheet melts into the oceans.