Sorry for the lack of messages about the trip the past four days...We've been working hard!
After our initial first successful half coring day of 4 m, we followed it up with three more successful coring days. We extended the initial 4 m deep hole down to 5 m. This site is in a very old drained thaw lake basin. We stopped about 0.5 m above sea level because the SIPRE coring become pretty difficult and coring at those depths with the system is risky because it's easy to get the barrel stuck in the ground.
From the DP-1 coring site, we transited about 1.5 km to the east and retrieved a 4 m core in a relatively (300 yrs ago or so) drained thaw lake basin. We also stopped about 0.5 m above sea level at this site that sits a little bit lower than Dp-1.
From the DP-2 coring site, we cruised along the sea ice about 6 km further east to Point McLeod. PM is a primary surface, not having been reworked by thermokarst lake formation and drainage during the Holocene. This site is amazing. The bluffs are about 7 m above sea level and extremely ice-rich permafrost. At this site we were able to core down to 6.2 m using the SIPRE barrel system but could not penetrate any deeper. Interestingly, this is also about 0.5 m above sea level. To help fill in the time before Go and Chris and the other coring system arrived we collected some shorter core material. Average core material retrieval over the four days of coring was 4.5 m.
Go and Chris arrived from Barrow on Friday the 13th following our trail from earlier in the week for the most part. They made it to the TLO in just over 4 hrs which is pretty amazing transit time for the 80 mile run between Barrow and here. So now our camp is 5.
Unfortunately, Go's coring system took a beating and had a make over of sorts on the ride out. He was able to tinker and piece it all back together during the night and had it ready to go by morning. We also half broke our two SIPRE barrel engines the past week so Allen spent the evening making small engine repairs. Both are back in decent and sufficient working order.
So we setup Go's coring system at PM-1 today. The hole depth at the start of the day was 6.2 m and at the end of the day it was only 7.4 m deep. So the 1.2 m core material retrieval bumped our daily average core material retrieval rate down quite a bit. But as Misha said, sometimes 1 m is more interesting than 4 m....
At 6.5 m down the hole (0.5 m above sea level), the permafrost went from frozen to unfrozen. While the temperatures as this depth are roughly -7 C right now the soil is thawed because of the high salinity in the cryopeg sediments. The sediments remained unfrozen from 6.5 m down to 7.4 m, currently the bottom of the borehole. Tomorrow we'll try to use our lake talik probe to measured the depth of this cryopeg from the frozen ground surface.
The presence of the cryopeg just above and below modern sea level at the PM-1 site has us excited to extend the core hole depths at Dp-1 and Dp-2 core sites that have lower surface elevations but similar tricky core depths relative to sea level. Our best guess is that we'll also discover this cryopeg at the sites located 6 and 7.5 km to the west. The discovery of the cryopeg at Point McLeod also has us thinking of potentially interesting explanations for well documented increase in erosion at Drew Point...More to follow in the coming days....
On a more straight forward note, Chris measured ice thickness on our standard CALON/ALISS lakes today. The mean ice thickness this year is 1.2 m and is the thinnest lake ice thickness measured in this region by us since we started working here in 20o7 and compared to 2.3 m in 1976. This is in line with our fairly well documented thinning lake ice trend on the Arctic Coastal Plain. This year it appears to be combination of a record warm winter on the North Slope and the 30 to 40 cm of snow cover on the lake ice surfaces.
It's exciting to be involved in such interesting research in this beautiful landscape!
Try to be more informative over the next days. Here's some photos in the meantime.