ALBERT

Description: Pine Island Glacier currently experiences the largest negative ice sheet mass balance in comparison to other outlet glaciers in Antarctica and hence is the largest contributor to modern sea-level rise. Ice loss of this glacial outlet and neighbouring ones has increased greatly over the recent decades through ice thinning and flow acceleration that also resulted in rapid grounding line retreat, most likely as a result of basal melting induced by the inflow of warm Circumpolar Deep Water onto the shelf. Due to the glacier’s topographic setting, a bed that deepens beyond the grounding line to the deep interior basin of the West Antarctic Ice Sheet (WAIS), it has been suggested that this increased ice loss may be a precursor of WAIS collapse. Despite the increased mass loss, however, the calving front of Pine Island Glacier remained more or less stable in a position west of a pinning point located at the northern part of the glacier and its orientation remained similar (10-30° east of north) since the earliest observations in the mid-20th century. Large icebergs where calved at intervals of a few years, e.g. the B-31 calving event (720 km²) in November 2013, but subsequently the calving front re-advanced close to or even beyond its former position. In 2015 this pattern changed with a calving event initiated by a large rift oriented 55° east of north and the calving front for the first time retreated east of the pinning point. The rifts that initiated this calving event were proposed to have formed by expansion of basal crevasses due to ocean forcing. In 2017 we were able to access the formerly ice-shelf covered area during RV Polarstern expedition PS104. Bathymetric data from this area revealed a bathymetric knoll with minimum water depth of ~375 m that was the former pinning point of the glacier. A new rift 8-9 km upstream of the calving line that may initiate the next calving event within a year was visited by helicopter. Satellite data acquired in the last decades suggest that unpinning from the bathymetric knoll likely took place in 2006. We use these data collected during expedition PS104 in combination with the satellite data to investigate the impact of glacier unpinning on Pine Island Glacier calving dynamics.

Description: In recent years several previously undiscovered grounding-zone wedges (GZWs) have been described within the Abbot-Cosgrove palaeo-ice stream trough on the easternmost Amundsen Sea Embayment shelf. These GZWs document both the Last Glacial Maximum (LGM; 26.5-19 cal. ka BP) grounding-line extent and the subsequent episodic retreat within this trough that neighbors the larger Pine Island-Thwaites trough to the west. Here we combine bathymetric, seismic, and geologic data showing that 1) the grounding line in Abbot Trough did not reach the continental shelf break at any time during the last glacial period, and 2) a prominent stacked GZW constructed from six individual wedges lying upon another was deposited 100 km upstream from the LGM grounding-line position. The available data allow for calculating volumes for most of these individual GZWs and for the entire stack. Sediment cores were recovered seawards from the outermost GZW in the trough, and from the individual wedges of the stacked GZW in order to define the LGM grounding-line extent, and provide minimum grounding-line retreat ages for the respective positions on the stacked GZW. We present implications of a grounded-ice free outer shelf throughout the last glacial period. Furthermore, we assess the significance of the grounding-line stillstand period recorded by the stacked GZW in Abbot Trough for the timing of post-LGM retreat of the West Antarctic Ice Sheet from the Amundsen Sea Embayment shelf.

Description: The cores and dredges described are taken during the R/V New Horizon RISE III Expedition from April until May 1979 by the Scripps Institute of Oceanography. A total of 36 cores and dredges were recovered and are available at Scripps Institute of Oceanography for sampling and study. The goal of this expedition was to accomplish the field work of a combined field and laboratory study aimed at increasing the understanding of the origins and development of young oceanic volcanoes.

Description: Submarine photography and box cores described in this report were taken during the R/V Oceanographer Cruise RP-8-OC-75 in October-November 1975 over areas A, B and C of the DOMES project (Deep Ocean Mining Environmental Study). This cruise was part of Phase I of the DOMES project which was conducted by the U.S. Geological Survey under the auspices of the National Oceanic and Atmospheric Administration (NOAA). The purpose of DOMES project was to acquire the information necessary to provide both a timely and an independent assessment of the impact of deep ocean manganese nodule mining on the marine ecosystem before commercial mining operations begin. It was formulated in cooperation with the academic community and the mining industry. It consisted of a two-phase study, first to obtain basic information on the deep ocean environment and then to assess the impact of prototype mining operations on that environment.

Description: Submarine photography and box cores described in this report were taken during the R/V Oceanographer Cruise RP-8-OC-76 in October 1976 over area C of the DOMES project (Deep Ocean Mining Environmental Study). This cruise was part of Phase I of the DOMES project which was conducted by the U.S. Geological Survey under the auspices of the National Oceanic and Atmospheric Administration (NOAA). The purpose of DOMES project was to acquire the information necessary to provide both a timely and an independent assessment of the impact of deep ocean manganese nodule mining on the marine ecosystem before commercial mining operations begin. It was formulated in cooperation with the academic community and the mining industry. It consisted of a two-phase study, first to obtain basic information on the deep ocean environment and then to assess the impact of prototype mining operations on that environment.

Description: Information on possible resource value of sea floor manganese nodule deposits in the Pacific has been assessed by Deepsea ventures Inc, from the collection of manganese nodules and crusts obtained during past research vessels' cruise from the Scripps Institution of Oceanography.

Description: The cores described in this report were taken on the SOUTHTOW Expedition in June 1972 to January 1973 by the Scripps Institution of Oceanography from the R/V Thomas Washington. A total of 105 cores and dredges were recovered and are available at Scripps for sampling and study.