Text

theses

Aridity is an important component of climate change. Wildfires linked to dry conditions can drastically alter the biomass of a landscape. Diagnostic molecules created in these fires during the incomplete combustion of plants can be used to estimate past biomass burning events. Biomass burning markers (BBM) were isolated from three sites from the South Island of New Zealand, and quantified using GCMS analysis. A record of fire occurrence based on these BBM revealed a pattern of increased aridity in the past. The central South Island was characterized by persistent dryness in the glaciation, increased wetter periods marked the Younger Dryas and Antarctic Cold Reversal, followed by drier cycles with fewer periods of wetness into the early Holocene, and persistent wetting toward the late Holocene. The southern end of the South Island showed consistent wetness from the mid Holocene to the modern. Dryness changing in longer vs. shorter and wetter vs. drier is a pattern seen from the glaciation through the early Holocene. Pollen-based temperature reconstructions in the study sites do not agree with reconstructions from elsewhere in New Zealand. These new results documenting burning in the glaciation and through the early deglaciation are a plausible explanation for bias in these temperature reconstructions due to local aridity in the study areas of the South Island. Changes in this local aridity were likely due to the Southern Westerly Winds, which shifted north during the glaciation, then overall shifted southward toward the Holocene.

ETD_6623

M.S.

Includes bibliographical references

by Lauren Meredith Weisel

doi:10.7282/T3028THG

ETD graduate

The author owns the copyright to this work.