LATE HOLOCENE GLACIAL STRATIGRAPHY OF COLUMBIA BAY ALASKA: EXTENDING THE RECORD



c
Figure 1: Calving margin of Columbia Glacier during the 2003 field season. (T. Lowell)

Project Overview

Project Abstract

Previous Research

Field Location:

Site Information and Sample Details:

Additional Resources:

Links for additional information on Dendrochronology, Glacial Geology, and other fun stuff:

Project Overview:

Supported by various sources The College of Wooster has been able to work with other institutions such as Columbia University (Lamont-Doherty earth Observatory), The University of Colorado (Institute of Arctic and Alpine Research), The University of Cincinnati as well as many other organizations to conduct field work throughout Alaska since the mid-1990's. The scope of this research has been to recreate climate histories through the use of dendrochronology. We have collected hundreds of tree samples that have provided insight into the periods such as the Medieval warming period, the Little Ice Age, and other climate changes occuring over the past  2,000 years. During the 2003 field season under funding provided by NSF grant 9910809*, Greg Wiles, Jim Figley (Cornerstone Elementary, Wooster Ohio) and Matthew Beckwith-Laube of the College of Wooster along with Thomas Lowell of the University of Cincinnati set out to Columbia Bay to examine and collect from two sites in the Columbia Fjord. The findings from this field season will be presented in a senior undergraduate thesis by Matthew Beckwith-Laube, at the 2003 Geological Society of America annual meeting in Seattle, Washington, and possible papers to come. This web site hopes to provied an adequate overivew of the methodsof dendrochronology as well as the background of study in Columbia Bay

Figure 2: North facing view of Columbia Bay and Columbia Glacier. Distance from the open ice in the lower right hand corner to the calving margin is roughly 15 kilometers. The glacier sat here, at its terminal moraine, since its maximum in the 1890's until it began a drastic retreat to its present position. (T. Lowell)

Project Abstract:

Columbia Glacier, one of the largest tidewater glaciers in the northern hemisphere, began a drastic retreat from its terminus in 1979 where it had remained for over a century. The glacier has thinned over 300 hundred meters and retreated 13 kilometers to its present calving margin. This drastic retreat has uncovered a previously buried Mountain Hemlock forest that was run over by advance of the glacier. Preliminary tree-ring dating of the outer ring of tree sections collected in the Summer 2003 from up-fjord sites within 1 km of the present calving margin reveal glacial advance dating to the early 11th Century A.D. with outer ring dates ranging from 1020 and 1025 A.D. Seventy subfossil samples from 8 sites in the fjord are currently being analyzed and should provide details to this advance history. Estimates of advance rates from these up-fjord sites are consistent with previously tree-ring estimated rates of about 40 meters per year. In addition to logs obtained from these sites, wood samples are being radiocarbon dated to understand the complex glacial stratigraphy composed of superimposed till layers discovered during the 2003 field season. This stratigraphy could reflect earlier advance/retreat cycles and extend the glacial history prior to the tree-ring dated advance and observed retreat of the past 1000 years.

Previous Research:

This area represents a compilation of 5 years of field work and very successful and thorough data collection. We have aver 300 trees in various chronologies as well as dozens of samples yet to be processed. Work from our sites has been published in Quaternary , The Holocene, and various other major journals. The majority of previous research has focused on the influence of the North Pacific on climate variations.

Field Location:

With the following pictures, figures, and text, we aim to provide a solid background about our field sites. It is only with a sufficent background that we can fully understand what we are attempting to do at our field sites in question as well as Columbia Bay as a whole..

Figure 3: Columbia Bay Field Sites since 1997. Each red dot represents a field site with an outter ring date from a sub-fossil log. Grey dots represent a living tree that was sampled. From the 2003 field season we have found outter rings to average around 1018 A.D. With these dates we can calculate rates of advance for the advance leading up to the 1808 terminus (Figure from Megan Kennedy)



Figure 4: Aerial view of Columbia Bay in 2000. The gold dots represent the two most recent sample sites.
 Our site is the northern most site yet sampled in the Columbia Bay.(B. Molina)

Site Information and Sample Details:

In order to keep samples organized and sites seperate, i entered all my data in to this Excel Spreadsheet of Sites and Locations.
This spreadsheet contains all available GPS readings, altitude information, inner and outtter ring dates, as well as any pertenant information reguarding our sites. Also to maintain seperation between samples and sites i have plotted each sites information (sample size, elevation, outter ring dates, and site number) onto a digital picture of sites CG-03-3 and 4.

 This will enable us to run several models looking at the behavior of advancing ice, mainly thickening rates and modes of advance. We hope to see a succession of dates ranging from site to site (bottom to top of the valley). If we see progressively older outter ring dates up valley then we can deduct that the ice was thickening up valley as it advanced. On the other hand, if we see progressively younger dates up valley then we can deduct an advance of ice downvalley coming from above.  This model assumes that logs have been preserved in place and have not been transported a great distance. Another possibilty arises if we get dates that do not display any pattern. If this is the case we can assume that either logs have been transported or the ice did not simply thicken up or down valley. There could be a variety of movements that occured to deposit the till and logs in question. Further examination will provide additional clues as to the depositional history of this valley.
    As we continue our examination of these sites we develop more and more ideas about what has been going on in this dynamic area. In the coming months i hope to continue with the construction of a master chronology of the area, determine advance rates, advance 'style', and possible figure out what these ideas mean both locally and globally.
h






Figure 5 (right): This image represents the seperation between sub-sites at site 4. Each site has a corresponding altitude, sample size, and site number located in the enclosing box. In coming weeks, it is my aim to also include outter ring measurements for each site to try and determine the mode of advance within this valley. (T. Lowell)
                                                                                                                                                                                                                                                                                                                                                                           



Figure 6: Logs located at site CG-03-3.3. This is a somewhat typical assemblaged of logs suspended in glacial till. As you can see, the logs show no solid indicators of glacial direction or prior growth area. It is encouraging to notice the abundance of root matter that could suggest minimal transport of the logs. In several samples pine needles and organic rich soil accompanied the logs. This also suggests minimal movement. (T. Lowell)

Figure 7 (below): This image from site 4.2  is of organic rich soil with intermixed hemlock needles. This is encouraging to see becasue it suggests little transportation of materials after the glacier uncovered this site. We believe that this norhtern most site has been uncovered very recently, possible less than 1 year.
 (M. Beckwith-Laube)



Figure 8: This image is facing northeast looking up valley at site 4.3 and 4.4. Notice the two distinct log assemblages that define this valley. The closer log assemblage, site 4.3 was situated on a bedrock knob that constricts the valley greatly. Site 4.4 at the top of the picture is situated just below a bedrock outcrop. Site 4.4 is drastically different in that it is constricted by a flat run of the valley. There is more till and other material clogging this area. (M. Beckwith-Laube)

About Me:

My name is Matthew Beckwith-Laube and i am a senior at the College of  Wooster and i will graduate (hopefully) this spring. My research interests are global climate change over the past 20,000 years (give or take a few thousand) and the role glaciers and other bodies of ice and oceans have in this global change. It is very important to understand what has been going on around us since humnan civilization took root. It is interesting to see what we are doing to our world to change the dynamics of our climate. Feel free to email me (Mbeckwithla@wooster.edu) with any corrections, complaints, or suggestions that will assist me in my thesis or thoughts on this issue.
Figure 9: I am on the left and my advisor, Dr. Greg Wiles is on the right. In the back ground is the calving margin of Columbia Glacier. The ice directly behind us is dead ice that has been left behind as the glacier has retreated. This picture is just over a small hill from our camp, so the ice margin was only a few hundered meters from our camp. (M. Beckwith-Laube)



















Additional Resources:

Here is my Power Point Presentation from my Fall 2003 Geology Club Presentation. It provides an overview as to the objectives, methods, and prelimenary findings of this project. In the coming months I will post my chronology of Columbia Bay, some neat graphs, and additional information as I develop this topic.

Links for additional information on Dendrochronology, Glacial Geology, and other fun stuff:

The College of Wooster Geology Links
 The University of Cincinatti
 The Tree-Ring Society
 Lamont-Doherty Climate Links
 The University of Tennesse
The University of Arizona, Tuscon Arizona
 NOAA
 PAGES
 World Climate Research Programme: Climate Variability & Predictability
 International Tree-Ring Data Bank


Geological Society of America
 Era Helicopters



*This material is based upon work supported by the National Science Foundation under Grant No. 9910805. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.