Labwork

Lab-work webpage update
The marine geology team collected 54 gravity cores, 7 multicores and 4 box cores during the two Polarstern cruises (PS100 and PS109) in 2016 and 2017. In the summer of 2017, the onshore team collected a further 4 piston cores and 11 surface cores from the epishelf lake Blaso as well as one core from a freshwater lake in the region. Since these expeditions, a vast amount of analysis has been conducted on these cores. The following lists the methods so far used on these cores.

1 Physical properties analysis
All core passed through the Geotek multisensor core logger where we collected:

• Magnetic susceptibility
• Wet bulk density
• P-wave velocity
• Electrical resistivity

Once split, all cores were visually logged, photographed and shear strength measurements taken using a handheld torvane. X-radiographs were collected for each core on our Geotek X-ray CT Core imaging system.

We used the information collected on these instruments as well as the visual logs to prioritised further analysis on selected cores. We scanned these priority cores using the Geotek X-ray Fluroesence (XRF) logger, which provides high-resolution elemental abundance data of the core material. Further analysis also included water content measurements and particle size analysis that was conducted on the Beckman Coulter laser diffraction particle size analysers.

Combined, the information collected above allows us to characterise the sedimentary signature of the NE Greenland Ice stream, including the subglacial sediments as well as the deglacial sediment record.

2 Palaeoenvironmental reconstructions and organic geochemistry analysis
On selected cores, foraminifera assemblage counts have been used to reconstruct oceanographic changes since the Last Glacial Maximum from offshore NE Greenland. Additionally, we have collected δ18O and δ13C data on both planktic and benthic foraminifera that will provide further information on the changing water masses during the deglacial period. Using the Analytik Jena Multi EA (Elemental Analyser) 4000, we have measured the Total Carbon (TC) Total Inorganic carbon (TIC) and calculated the Total Organic Carbon (TOC) content in selected cores.

The epishelf lake Blaso and the fresh water lake cores have had further analysis conducted on them. This includes chironomid analysis, which will provide a temperature reconstruction from the lake core, as well as organic geochemistry analysis.

Combined, this multiproxy approach will give us detailed information on the oceanographic and climatic changes that occurred in the region over the past 20,000 years.

3 Geochronology
Robust chronology is key if we are to constrain the timing and pace of change of the NE Greenland Ice Stream, as well as the timing of oceanographic and climatic changes since the Last Glacial Maximum. Radiocarbon dating of foraminifera and marine mollusc has been our primary method and we now have 64 radiocarbon dates collected from across the shelf. In the upper sections of the core we have used 210Pb and 137Cs dating method to constrain the more recent changes recorded in the sedimentary archive.

The data we have collected, and continue to collect, will provide the most detailed reconstruction on the largest ice stream to drain Greenland to date. This data is imperative if we are to understand the processes and mechanism acting upon arctic ice streams and to put present day change into context.