Traces of Impact: multi-proxy analyses of major storm signatures in New Hampshire lake sediments
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Authors
Tifft, William
Date
2020-11-20
Type
Thesis
Language
en
Keywords
non-tropical storms, climate change, hazard mitigation, instrumental meteorology in New England, sub-catastrophic but high-impact events
Alternative Title
Abstract
Description
AN ABSTRACT OF THE THESIS OF
William D. Tifft for the degree of Master of Science in Environmental
Science and Policy presented on November 20, 2020
Title: Traces of Impact: multi-proxy analyses of major storm signatures in New
Hampshire lake sediments
Abstract approved:
Lisa A. Doner
Major tropical and non-tropical storms cause extensive damage throughout the
Northeast U.S. Recent climate change may be driving increases in their
frequency, but large uncertainties exist around average return-intervals of so called 50-year, 100-year and larger storms, because of gaps in the historical
record. Effective community resilience plans, especially for hazard mitigation,
rely on the accuracy of the century-scale storm record, but instrumental
meteorology in New England began in the late 1800s, too short a time for
prediction of rarer, stochastic events. Longer records, that improve the
accuracy of long-term storm frequency data, encompass varying climate
regimes, and identify sub-catastrophic but high-impact events, will enable
communities to better anticipate and mitigate storm effects. To improve
documentation of major storms, and to test several hypotheses about the
sensitivity of lake sediment archives to storms of varying intensities, I develop
and compare four new paleolimnological data sets in central New Hampshire.
This research primarily asks, do major storms, documented in meteorological
and historical records as destructive and highly impactful, leave distinctive
traces in lake sediment records? It also asks: what magnitude or duration of
storm is needed to create a trace in the sediment record; do storm traces vary across watersheds experiencing other types of disturbance; are storm
signatures consistent from watershed to watershed; do storm frequencies vary
across climate regimes; and which analytical practices best capture storm
histories across multiple lake basins? I address these research questions
using new 210Pb-dated sediment core records from four central New
Hampshire lakes: Norway Pond, Hancock; Pleasant Lake, Deerfield; Spofford
Lake, Chesterfield; and Newfound Lake, Bristol and the list of major storms
included in the 2013 State of New Hampshire Multi-Hazard Mitigation Plan.
Sediment datasets include loss-on-ignition, dry bulk density, magnetic
susceptibility, particle-size, stable isotopes, and geochemistry. Although time
series of these datasets fail to show coherence around known storm events,
multi-variate statistical analyses, including analysis of variance (ANOVA),
principal component analysis (PCA), and binomial regression analysis, show
that, in all the lakes except Pleasant Lake, there are statistically significant
storm-coincident sediment changes. The ANOVA results indicate that zinc and
lead are significantly different (0.05 confidence) between storm and non-storm
events in all four lake records, and other heavy metals: Ba, Cd, Fe, Mn, Ni,
and S, and High Frequency Mass Susceptibility are significantly different
between storm and non-storm events in three of the four lakes. The PCA
results reveal that the association of variables changed over time, with storms
of the last 30-years clustering near each other. The binomial regression
supports the concept that it is possible to use individual variables to identify
the presence or absence of major storms in each sample. This technique has value for deriving the minimum long-term frequency of major storms in a given
region.