Date of Award

Winter 2023

Document Type

Thesis (Master's)

Department or Program

Earth Sciences

First Advisor

Erich Osterberg

Abstract

Wildfires have become more destructive over recent decades with climate change, so understanding how fire regimes will change with further climate change is critical for effective fire management practices. Paleofire records provide insight into how fire regimes have responded to temperature and precipitation variability in the past. Ice cores, such as the Denali ice core from central Alaska, capture regional-scale fire proxies including black carbon at an annual resolution for centuries to millennia. This makes them ideally suited to construct high temporal resolution, regional paleofire records extending back into the Common Era. However, it is critical to understand the instrumental wildfire record, its relationship with instrumental climate variability, and evaluate how well it is preserved in the ice core so as to properly interpret the longer history of wildfire-climate relationships in the ice core record. Here we use atmospheric back trajectories, gridded precipitation data, and instrumental wildfire records to demonstrate that large wildfires from central Alaska are most likely to be preserved in the Denali ice core. We statistically evaluate relationships between various instrumental wildfire metrics such as the number of Alaskan fires and area burned in a given year, and find statistically significant relationships with Denali ice core wildfire proxies. Our climate analysis indicates that Alaskan wildfires are correlated with anomalously warm and dry conditions associated with a high-pressure ridge in the 30 days prior to ignition. Large and small Alaskan fires have similar (p > 0.1) temperature and precipitation conditions prior to ignition, but large fires are associated with significantly drier (p < 0.001) conditions than small fires after ignition. Compared with small fires. large fires are also associated with significantly more (p < 0.05) sea-level pressure variability both before and after ignition. This instrumental wildfire and climate analysis will enable the study of changes in summer climate and wildfire activity in Alaska over the past 1200 years from the Denali ice core. This paleofire record will allow for a better understanding of how Alaskan wildfire is expected to change in the near future.

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