Archive for June 12th, 2015

John Muir, Alaska, and A Tree Mountain Chronology

June 12th, 2015

Guest Blogger: Audrey Steiner-Malumphy

In 2011, Dr. Wiles and his advisees Lauren Vargo and Jennifer Horton cored dozens of trees from Tree Mountain in Alaska’s Glacier Bay National Park and Preserve. Muir Glacier is located northwest of this mountain, named after the esteemed naturalist and preservationist John Muir.

John Muir in Sierra Nevada, courtesy of PBS.

John Muir in Sierra Nevada, photo courtesy of PBS.

Muir first traveled to the area in 1879 with a particular interest in Alaska’s glaciers. He returned many times, continually fine-tuning his preservationist vision while drawing from theistic and transcendentalist ideas to transform the public’s perception of wilderness. Muir’s published works recalling these expeditions sparked national interest in Alaska’s wilderness and its preservation, laying the foundation for environmental debates yet to come.

Map of Glacier Bay, edited by John Muir. Published in the book Alaska Days With John Muir.

Map of Glacier Bay, edited by John Muir. Published in the book Alaska Days With John Muir.

Though the Tlingit lived in the Glacier Bay region for centuries, and others explored the area before him, Muir was the first distinguished scientist to map it and record his observations.

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Above is a present-day map of Glacier Bay, courtesy of Google Earth. Tree Mountain is marked in red on the southern border of Adams Inlet, which feeds into Muir Inlet. Muir Glacier lies at its base. Note the altered position and size of the glacier in comparison to Muir’s map.comparison

Photographs from the National Snow and Ice Data Center famously portray Muir Glacier’s retreat. Between 1941 (left) and 2004 (right), the tidewater glacier retreated more than seven miles, though it has been rapidly retreating since the end of the Little Ice Age in the mid 1800s.

Photograph of Muir Glacier from Alaska Days With John Muir.

Photograph of Muir Glacier from Alaska Days With John Muir.

Muir observed the rapid retreat of glaciers, expressing concern for Alaska’s changing climate and frustration with potential anthropogenic causes, specifically deforestation. In October of his 1879 expedition, he wrote in his journal, “That the climate is warmer is shown by the melting shrinking condition of the glaciers… where formerly much snow fell to thaw off gradually, incessant flood-rains fall, saturating the soil, causing it to decay and become slippery and wash off… It was not in this condition while the forests existed.”

Muir’s 1895 journal sketch of Muir Glacier from Tree Mountain.

Muir’s 1895 journal sketch of Muir Glacier from Tree Mountain.

To learn more about the climate in the Glacier Bay area when Muir recorded his observations, I measured the tree-ring widths of the Tree Mountain cores. Twenty of the Tree Mountain samples dated back to the mid 1800s or later, allowing me to compare tree-ring records with John Muir’s notes from his 19th century expeditions.

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The growth patterns of tree-rings vary based on the species, age of the tree, and other environmental factors. However, tight growth patterns, representing little growth, are typically an indication of stress. Increased growth usually reflects temperature, precipitation, the availability of nutrients.

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This figure above shows the standardized raw ring widths of the twenty cores from Tree Mountain. The growth trend has been removed. The blue line beneath the raw data represents the number of cores measured each year.

charttA 2014 study headed by Dr. Wiles provides a chronology and climate reconstruction for the entire Gulf of Alaska over the past 1200 years.

According to my Tree Mountain findings, John Muir’s 19th expeditions in Alaska occurred during a period of gradual warming, aligning with the chronology provided in Dr. Wiles’ study. However, the small Tree Mountain sample size poses difficulties in making significant comparisons, as well as the complexities of the numerous factors that influence both ring width and temperature, which are not accounted for in this post. Further comparisons of the paleoclimate record and the writings of John Muir in Glacier Bay continue..

Russian Birch Climate Reconstruction- Part 2

June 12th, 2015

Guest blogger- Clara Deck

This summer, I am working with Dan Misinay to continue a dendrochronology project focused on Kamchatka, Russia. We have been working with birch tree cores (Bertula ermanii) collected from the region by Dr. Wiles and I.S. student Sarah Frederick in the summer of 2014.

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Our goal is to use the cores to gather information about the climate. By counting, measuring and comparing different cores, Dan and I developed separate tree ring width chronologies from different areas in Kamchatka.

Kamchatka Peninsula GE

My samples are labeled NR in the northern part of the Kamchatka peninsula, while Dan’s are labeled UG. SANO represents birch cores in a study by Sano et al, 2009. The UG and SANO data correlates very well together, but the NR data is in a much different latitudinal location, and does not correlate. With the Sea of Okhotsk to the east, the Pacific Ocean to the West, and numerous mountain ranges and volcanoes, there are many climate factors that may influence the growth of these trees along the peninsula. The following work deals solely with my samples (NR).fulltabs

Shown here in green is the standardized data for the entire chronology (1823-2014). Trends in this graph may indicate climate signal and will be further analyzed this summer. The blue line represents the number of samples for each given year.

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I compared my tree ring data with meteorological data from a nearby weather station in Kljuci, Russia (also spelled Klyuchi). This graph shows the correlation of the tree rings with the minimum temperatures for each month. Months from the previous year are labeled t-1, while the present is year t. High positive correlations are shown during March through August of the present year, indicating that minimum temperatures in these months primarily influence the tree ring widths. Though this graph only shows correlations with minimum temperatures, I found the same trend with maximum and mean temperatures.

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The map above shows a zoomed in region of northeast Kamchatka with spruce (Picea) and larch (Larix gmelinii) samples from a study called Constraining recent Shiveluch volcano eruptions (Kamchatka, Russia) by means of dendrochronology (Solomina, et al 2008). Shiveluch volcano is adjacent to the site where the birch tree samples were collected, and all of the samples shown could be affected by its volcanic activity. It is one of the most active volcanoes in Kamchatka, and a significant eruption was recorded in 1964 (Solomina, et al 2008). The tree ring record should show evidence of this eruption in the year 1965. The study indicated that although a slight decrease was shown in their cores, it was of negligible scale and does not provide clear evidence of the eruption. I am interested to see if my samples show evidence of the eruption, because of its different position relative to the volcano.

1965

Shown here is isolated data from 1950-1980 from the above shown chronology, and shows a drop off in ring width growth in 1965. This could be evidence of a volcanic eruption, but as you can see even in this small data set, variability like this is not uncommon. More work needs to be done to determine the significance of this decrease.

 

References:

Sano, M., Furuta, F., and Sweda, T., 2010, Summer temperature variations in southern Kamchatka as reconstructed from a 247-year tree-ring chronology of Betula ermanii: Journal of Forest Research, v. 15, p. 234–240, doi: 10.1007/s10310-010-0183-z.

Solomina, O., Pavlova, I., Curtis, A., Jacoby, G., Ponomareva, V., and Pevzner, M., 2008, Constraining recent Shiveluch volcano eruptions (Kamchatka, Russia) by means of dendrochronology: Natural Hazards Earth Systems Sciences, doi: 10.5194/nhess-8-1083-2008

Goodygoody Girdwood Chronology Construction

June 12th, 2015

 Guest bloggers: Kaitlin Starr and Maddie Happ
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Forest surrounding Girdwood, Alaska. Living mountain hemlock trees were cored from this site (Wiles, 2014).

    During the summer of 2014, the Columbia Bay team (Dr.Wiles, Nick Wiesenberg, Kaitlin Starr and Jesse Wiles) cored numerous trees near the town of Girdwood, Alaska. The collection is primarily made up of cores taken from living Mountain Hemlock trees from the surrounding forest. In addition to the living forests a few cores were taken from subfossil wood at Turnagain Arm.
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Kaitlin Starr coring a living Western Hemlock found in the forests surrounding the town of Girdwood (Starr, 2014).

    The Girdwood living tree collection was brought back to the Wooster Tree Ring Lab where the cores were mounted, sanded, counted and measured. Students, Maddie Happ and Kaitlin Starr constructed a chronology out of 38 cores sampled. The chronology spans 342 years, beginning at 1672 and extending to 2014. When compared to the established Turnagain Pass chronology by Jacoby, G.C., D’Arrigo, R.D., Buckley, B., our new Girdwood chronology correlated well. In addition, our chronology extends the known database for the region by contributing an additional 85 years of data.
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Girdwood core sample illustrating both tight and normal growth patterns. Growth patterns may vary due to shifting climates. Tight growth often occurs during periods of distress, such as drought or storms.

    The graph below illustrates the standardized tree ring measurements by removing biological growth trends from   the series. Removing growth trends allows us to view the desired climate signal.
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Standardized Girdwood chronology note the upward trend in the series . The red line indicates the sample size.

The chronology was compared with meteorological data from the nearest station, Anchorage (International Airport) and correlations are plotted below. We found an unexpected high negative correlation between our chronology and the minimum temperature data, specifically throughout the summer months (June, July and August). The possible cause of this correlation is unknown at the moment.

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This graph illustrates the overall correlation between tree ring width and mean temperature and precipitation in Girdwood, Alaska for the dendroclimatic year.

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The above graph displays the overall minimum temperature compared to the tree ring widths for Girdwood, Alaska. A clear significant negative correlation exists for the months of May, June, July, and August.

 

 

Taking a break to see York

June 12th, 2015

1 Mae Meredith SW York MinsterSCARBOROUGH, ENGLAND (June 12, 2015) — Team Yorkshire went on a holiday today with a visit to York, only a short train ride inland from Scarborough. We needed a break, and in any case the tides were not in our favor at Meredith’s Independent Study field site. It was another extraordinarily warm, clear and dry day. (Unlike the cold, foggy and damp Scarborough we returned to in the evening.)

Above Meredith and Mae stand in front of the southwestern portion of the iconic York Minster.

2 Mae Meredith York StreetHere we are walking down a York street. The city felt very large and busy after our days in Scarborough.

3 River Ouse in York from Skeldergate Bridge 585The River Ouse in York from Skeldergate Bridge. This river divides the city and has been an important transportation and trade route for centuries.

4 Constantine 061215This statue of the Roman Emperor Constantine the Great is a monument to his accession to the office in 306 CE while in York, then known as Eboracum.

We spent time at the Viking archaeological center (Jorvik) and the York Castle Museum before taking the train back “home” to Scarborough. It was a great cultural excursion as we prepare for our last days of fieldwork.