Tree-Ring Talk

A JOINT INSTITUTE OF THE ENVIRONMENT/LTRR SEMINAR: Volcanic Effects on Climate in the Late 20th and Early 21st Centuries

The relatively muted warming of the surface and lower troposphere since 1998 has attracted considerable attention. One contributory factor to this “warming hiatus” is an increase in volcanic cooling over the early 21st century. Our recent research has identified the signals of late 20th and early 21st century volcanic activity in multiple observed climate variables. Volcanic signals are statistically discernible in spatial averages of tropical and near-global sea-surface temperature, tropospheric temperature, net clear-sky short-wave radiation, and atmospheric water vapor.

Dendrochronology and middle Miocene petrified oak: Modern counterparts and interpretation

This study reports the first successful statistical ‘crossdating’ among ring width time series from many specimens of petrified wood, based samples of the genus Quercus from the Stinking Water (SW) site in Oregon, a Miocene-aged exposure associated with the Columbia River Basalts. Ring width time series from 26 radii, 17 different trees, show significant intercorrelation.

Probing (into) the memory of trees with dendrochronology

Communicating with trees through dendrochronology involve developing observational skills that goes beyond the usual year-to-year changes in ring width. Developing excellent observational skills is at the core of crossdating and dendrochronology. Understanding how tree-rings are affected by environmental factors also allows their use in reconstructing conditions prior to the onset of instrumental records. In this talk, I will briefly cover a few research projects being pursued at the University of Winnipeg DendroEcology Laboratory (UWDEL).

Asian Monsoon Variability over the Past Millennium Reconstructed from Long Tree-Ring Records: the Monsoon Asia Drought Atlas, version 2 (MADAv2)

The Monsoon Asia Drought Atlas, version 2 (MADAv2), is a substantially updated and improved year-to-year reconstruction of summer drought and wetness on a 1.0° grid over Monsoon Asia. It has been developed using the same basic methodology as that used in producing the previous version (MADAv1) published in 2010 and is now based on an improved target field of self-calibrating Palmer Drought Severity Indices (scPDSI) and a significantly larger network of 453 tree-ring chronologies compared to the previous effort.

Despite increasing aridity, climate change promotes growth of North American grasslands

A grassland productivity model, based on temperature-moisture interactions and informed by observations made across a range of North American grassland ecosystems, was used to predict the response to climate change based on CMIP-5 climate projections over the next century. I will present the results of the model analyses which indicate a future shift of grassland growth towards both earlier spring emergence and delayed senescence in autumn, which together compensate for drought-induced reductions in summer productivity in most North American grassland regions.

A new laboratory of dendrochronology in Valparaíso, Chile: Expanding the tree-ring applications in South America

The breadth of geographic conditions, climatic variations, and dynamics of the landscape of Chile makes Chile a natural laboratory for the use of dendrochronology in several of its applications. In this talk, we will share some of the experiences that are taking place in the new Laboratory of Dendrochronology and Environmental Studies in the city of Valparaíso to study the dynamics of the environment in Chile.

Tipping point analysis of geophysical data

We apply the tipping point toolbox [1-8] to study transitions and bifurcations in various geophysical datasets. We study early warning and detection signals of the records using methodology that combines degenerate fingerprinting and potential analysis techniques for anticipation, detection and forecast of tipping points in a dynamical system. Degenerate fingerprinting indicator is a dynamically derived lag-1 autocorrelation, ACF (or, alternatively, short-range scaling exponent of Detrended Fluctuation Analysis, DFA [1]), which shows short-term memory in a series.

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