Graduate student Ben Gaglioti and his advisor Dr. Mann are building on their previous successful NIWR project that looked into the changes of ancient Alaskan permafrost due to temperature and precipitation from 14,000 to 7,000 years ago. Their current project is filling in the missing years by investigating the release of carbon from thawing permafrost from 7,000 years ago to present. They hypothesize that ancient large mats of vegetation may insulate current permafrost and helping slow the thawing process. They will be testing their hypothesis by comparing oxygen isotopes of ancient willow wood to climate records.
Documenting the responses of permafrost to past climate change can greatly can improve our understanding of how permafrost and the hydrological regime that depends on it will respond to warming climate in the future. Here we propose to build on past NIWR-funded research (Gaglioti et al., 2014; In Prep) to assess the sensitivity of permafrost carbon release through thaw in arctic Alaska to changes in temperature and precipitation. Our previous work reconstructed how the release of permafrost carbon varied in response to climate changes during the intervals of 14,000 to 7000 years ago (14-7 ka) and from 1 ka to present. Here we seek funding to fill in the missing part of this record by obtaining new lake cores that span from 7 ka to present. Our previous results showed that permafrost carbon release was very sensitive to deglacial warming events, but not recent warming, which suggested that sometime after widespread peat accumulation (8 ka) buffered the underlying permafrost from subsequent warming. In this project, we hypothesize that as these surface organic mats spread and further insulated the ground, permafrost thaw events became less sensitive to climate fluctuations. We will test this hypothesis in two steps. First we will use the del18O values of ancient willow-wood cellulose to complete our time series of changing temperature and precipitation. This del18O time series of willow wood will be interpreted in terms of climate by using a geographic network of isotope-climate relationships observed on the modern landscape (previously funded by NIWR; Gaglioti, unpublished data). The second step in this study will be to obtain additional radiocarbon (14C) age-offsets from new lake cores that will fill in the missing part of our existing record of the release of ancient organic carbon from permafrost. This is a well-developed proxy for soil carbon release affected by permafrost thaw (Gaglioti et al., 2014). The climate records reconstructed from del 18O will then be compared to this age-offset record. This comparison will serve as a test for the hypothesis that the Holocene spread of organic mats buffered permafrost from episodes of warming air temperature, and that this same buffering effect is crucially important today in preserving the integrity of permafrost-carbon deposits on the North Slope.