Scott St. George

Rapid loess accumulation makes trees really dusty

Thu, 24 Sep 2009 23:00:23 -0400

I just returned from a ten-day trip to the Canadian Rockies to collect tree-ring samples and help a colleague studying wind-blown sediment transport. One of his study sites is located in the upper portion of the Athabasca River basin near Hinton, Alberta. This site produces an exceptional amount of loess, sediment that is mainly made up of silt and is transported by the wind.

I shot a brief video that shows how much dust piles up on trees growing downwind of one of the main loess production areas. It might look like the forest just needs a good cleaning, but the rapid build-up of loess also has important implications for local soil development and ecology. These systems may also serve as analogs to help us understand the dynamics of continental-scale dust production during the most recent glaciation.

PAGES poster on decadal drought

Thu, 13 Aug 2009 09:56:33 -0400

PAGES has asked participants from their recent 3rd Open Science Meeting to make PDF versions of their posters available for download at the PAGES website. I figured while I was doing that, I might as well upload the poster here too.

The title of our poster was ‘Using observations and proxies to assess the strength of decadal signals in North American drought’ and included work done by Toby Ault, David Meko and myself. Just click on the image to download the PDF.

Journal of Climate - Tree rings and Prairie drought

Thu, 26 Mar 2009 13:15:54 -0400

The Journal of Climate has published an article by myself and several collaborators that use tree-ring records to estimate how summer drought conditions on the Canadian Prairies have changed during the past 500 years.

The article is available for download at my ‘Publications’ page or at the journal’s website.

The regional drought reconstructions described in the article are available online at the World Data Center for Paleoclimatology. To obtain the data, visit their ‘Climate Reconstructions’ page and scroll down to the ‘Hydroclimate’ section.

Slide-of-the-day: Tree-ring prose from Roger Deaken

Fri, 27 Feb 2009 11:03:32 -0500

I have a new favorite quote about tree rings. Over the weekend, I came across a book review of Wildwood: A Journey Through Trees, written by the late Roger Deaken. The review includes a brief excerpt from the book that caught my eye:

A tree itself is a river of sap: through roots that wave about underwater like sea anemones, the willow pollard at one end of the moat where I swim in Suffolk draws gallons of water into the leaf-tips of its topmost branches every day; released as vapor into the summer air, this water then rises invisibly to join the clouds, and the falling raindrops ripple out into every tree ring.

The selection includes some beautiful language, but it’s also quite an accurate description of arboreal plumbing, the importance of transpiration, and the pathway that allows environmental signals to become encoded into annual growth rings. A lot of ideas fit elegantly into a single sentence.

Tree rings and drought in NRCan’s ‘Natural Elements’ newsletter

Thu, 12 Feb 2009 09:23:29 -0500

‘Natural Elements’, the online newsletter produced by Natural Resources Canada, has published a short summary of our article on tree rings and Prairie droughts that will appear in a upcoming issue of the Journal of Climate.

The article is available in English:
http://www.nrcan-rncan.gc.ca/com/elements/issues/33/trearb-eng.php

and French:
http://www.nrcan-rncan.gc.ca/com/elements/issues/33/trearb-fra.php