Allan Hills season complete; Final week at South Pole begins

Updates from Allan Hills Shallow Coring Team (I-187)

We have two weeks’ worth of updates from our ice coring team!

30 December 2023

This week the Allan Hills team continued ice coring and related projects. For those not following along on a weekly basis, originally I-187 planned to operate two drill rigs simultaneously, with two drillers, optimally collecting 4 approximately 200 m ice cores. The departure of driller Mike Jayred due to injury curtailed those plans. With one driller, only one core can be drilled at a time.

The first core drilled, using the 3 inch diameter Eclipse drill, was previously stopped at 90 m due to encountering a rock that could not be penetrated. This exploratory hole is in the region called the “Cul de Sac,” where previous shallow hand drilling revealed ice older than 1 million years near the surface. This week we took down the drill and drill shelter at this site and will not attempt more Eclipse drilling there this year.

The second core, using the 24 cm diameter Blue Ice Drill (BID), is ongoing near our camp. This is being drilled at a site where a previous exploratory hole (with a smaller drill) revealed 4.5 million year ice near the bed, at about 200 m. The purpose of the 24 cm diameter core is to obtain large samples of the oldest ice to allow co-registered measurements of age and a variety of environmental properties, including greenhouse gases and their isotopic composition. This second core has reached 130 m as of late afternoon today. We believe the ice at this site is approximately 180 m depth, but may be deeper. Recovering high quality core at Allan Hills is challenging with dry drilling equipment and requires drilling slowly and continually modifying parameters of the drill. We are not confident that we have enough time to finish this borehole this year and it may have to be reoccupied in another season. Elizabeth Morton is doing excellent work running the BID given that she has not operated it extensively before. (Jayred has more experience with this drill and made improvements during the last Greenland season, thus his departure was doubly unfortunate). Nonetheless, we are happy to report that core quality today was excellent and we are hopefully this will continue.

At the current depth we will begin sampling as much of the ice as is intact as possible, which will accelerate the pace of sample return. We appreciate the help of USAP Science Cargo in making the ice return process safe for the samples. Transport from the field site to Willy Field, and onward to the ice core storage facility requires a great deal of coordination when temperatures are warm.

Other activities at Allan Hills include:

Decision to return to Allan Hills in the 24/25 season. COLDEX had been considering moving operations to Elephant Moraine, but given logistical considerations (leaving material over winter at Allan Hills) and the slower than planned progress at Allan Hills, the field team and COLDEX leadership agreed that the opportunities at Allan Hills are better next season.
Sarah Shackleton, Julia Marks Peterson, and JM Manos spearheaded shallow drilling (IDDO and PICO augers) in the Cul de Sac region and near the current BID site, to, respectively, explore for other deeper drilling locations.
Abby Hudak conducted surface sampling in a shallow trench at the Cul de Sac region to better understand the complex stratigraphy there. Sarah and Julia, with ASC camp staff Emma Mayo, pitched in to tag team the last days of chain saw trenching.
Austin Carter, Asmita Banerjee and Ed Brook collected a large volume of ice containing a tephra layer near the Cul de Sac core site. Austin is now taking over one of the big camp water melters to separate the particles from the ice. The hope is to find enough K bearing crystals to do a Ar-Ar date.
JM Manos, with help from various others, completed all planned phase sensitive radar deployments and remeasurement and placement of stakes for flow velocity and ablation measurements.
JM also made two meteorite finds this week, bringing his total to 3. All will be passed on to ANSMET (they previously provided sampling kits).
We returned 11 ice core boxes returned to McMurdo by Twin Otter.
We had an amazing Christmas Eve dinner prepared by Ash and Emma, our camp staff (Halibut ceviche in Antarctica anyone?) a Yankee Swap gift exchange organized by Sarah, and lots of holiday cheer.
Christmas Day was a rare day off to recover from the rigors of Antarctic field work. Movie watching was the prime activity, with cinnamon rolls (Julia) and a 24-egg frittata (Ed) for Christmas brunch.

5 January 2023

This week I-187 (COLDEX) wrapped up ice coring and related projects at Allan Hills. Our 24 cm diameter ice core near the ice margin at Allan Hills reached a depth of 144 m. During the last few days of drilling core quality was variable, but useable samples were obtained from most drill runs. Elizabeth Morton (E) continued to vary drilling parameters to try to maximize core quality, but Allan Hills ice is tricky. We know from exploratory coring at this site that there should be approximately 40-60 m of ice below 144, with ages in this lower section up to 4.6 million years, and it is likely that I-187 will return to this site to complete the core in the 24/25 season.

Sarah Shackleton led collection of additional short cores with hand augers to explore for other old ice sites. One, in the Cul de Sac region, reached 11 meters. The second shallow core drilled this week was in the accumulation region at a site previously identified as a promising location for a 1 million year old deep ice core (~1250 m). This core reached 20 m, near the firn ice transition, and will provide valuable information about the depositional processes at this site. Julia Marks Peterson and Sarah measured the density profile in this core (spending several hours in the ice core storage trench).

Austin Carter also collected samples of a prominent volcanic ash layer in the Cul de Sac region, near the ice core site, melting many ice core boxes full of ice chips to extract several grams of sediment. We used the ash layer to measure the orientation of the complex stratigraphy at this site, finding dip angles between 30 and 50 degrees at the surface.

JM Manos continued geophysical measurements this week, including distributed temperature sensing in the borehole at the Cul de Sac core site and completion of GPS surveying of ablation stakes. JM and Ed also collected some reconnaissance samples for cosmogenic nuclide surface exposure dating – from a prominent moraine deposit near the Cul de Sac drill site.

Our last day of drilling was January 4. All remaining ice samples were retroed to McMurdo on January 5 with two simultaneous Twin Otter flights (24 ice core boxes). The team is now engaged in packing up camp, preparing cargo for Twin Otter and Basler flights, and storing supplies and equipment on site for work next season. A major task for the weekend is to take down the large Blue Ice Drill tent, pack up the drill and camp, and hope for good weather for the pull out!

We celebrated the new year with another fantastic holiday meal courtesy of Ash and Emma, champagne at midnight (generously provided by John Higgins before he left the camp in December), and a day off to recuperate from the rigors of field work on New Year’s Day.

Best wishes to all for the New Year from the Allan Hills! - Updates provided by COLDEX Director Ed Brook

Ice sculpture created from ice sections left over from cutting CFA sticks from shallow sections of the BID core ALHIC23-2.

Hanging bag containing tephra that Austin Carter separated from a large volume of melted ice.

Loading ice core boxes on the Twin Otter

Updates from South Pole Airborne Team (I-185)

After a very busy week of surveying in my last report, this week the gods of weather and statistical probability teamed up to shut us down, and if I had sent this report this early this morning I would have only two additional flights to report, dating back to last Saturday. However, I am happy to say that we are now flying our second flight of the day, and weather is looking good for a productive Saturday tomorrow. We have completed a dense corridor in the western part of our survey area, as well as our original 15 km grid from last year. All instruments continue to perform well.

As of today, we have six flights to go and six more survey days as we look to our delicate endgame to get our team and cargo back to McMurdo and make our flight off continent. In the mean time, we have been assessing data to prioritize our last few precious flights, realizing that it may be a long time before airborne geophysics returns to South Pole. However, it will not be a long time before COLDEX returns; we had the opportunity to tour the Heavy Science Traverse that had just delivered the fuel for next seasons COLDEX ground activities, and will return next season to support the Ice Diver melt probe and the surface geophysics campaign.

We also had an opportunity to share our science with the South Pole community, in a joint presentation by Duncan, Shravan, Shivangini and Megan, which had great interest and great questions from the crowd. We with KBA will be offering tours of the aircraft this no fly Sunday.

We look forward to a busy final week at Pole. Happy New Year y’all! - Duncan Young, University of Texas faculty member and Science co-lead for base operations and flight planning for project I-185