"We are looking at the historical photos and comparing them to the present conditions to get a good idea of the process and what happens when the climate in this particular region warms up," Hazlett said.
The region has been warming since the peak of the little ice age in 1750 when Glacier Bay existed as a single glacier.
Hazlett has worked on the project under United States Geological Survey senior researcher Bruce Molnia since 2003.
Each summer, Hazlett retraces the steps of early researchers and explorers, comparing photographs and studies from as far back as the 1880's to the present.
The historic photographs were obtained from government and university archives, historical publications, and old postcards purchased on Ebay.
However changes in the landscape make it difficult to match historical photographs to the land today.
"There are two things working against us," Hazlett said. "Vegetative succession and isostatic rebound."
Vegetative succession is the progressive growth of plants over time, from fireweed to spruce forests. Isostatic rebound defines the vertical land rise that occurs as glaciers recede.
"If you press on a sponge with your hand and then remove it, that rise is similar to what happens to the land when the glacier melts," Hazlett said.
In some areas the land rises at a rate of 3 centimeters (1.2 inches) each year. Over 125 years, the topography of the land has experienced a 10 to 11 foot rise.
This factor has made it difficult to use prominent landmarks from the historical photos, such as large rock outcroppings to identify the location.
The rapid revegetation further complicates the study. Thirty-foot cottonwoods now obscure the view where many historic photographs were taken.
Glaciers scrape the land, leaving bedrock as they recede, Hazlett said.
"Plant succession is a soil-building process as well as plant growth," she said.
Pioneer species like fireweed help to increase nitrogen in the nutrient-poor soil creating a habitable environment for low willows and alders. Alders continue to increase the soils nitrogen content establishing a base for cottonwood and ultimately spruce forest growth.
In 1916 William S. Cooper was the first person to study vegetative change and plant succession in Glacier Bay. He established and monitored 60 sites. This is the first study revisiting his sites.
"We have found amazing differences. In places where bare rock was recorded we are now finding spruce forests. In other places, things here hardly changed in almost 100 years," Hazlett said.
In Johns Hopkins Inlet the vegetation hasn't changed. Hazlett found the area is still covered with small plants, such as fireweed, willow and alder.
These pioneer species are the first to grow in the nutrient-poor soil, and are indicative of the early stages of plant succession.
There are several reasons why this area may be stagnant, Hazlett said. The fjord is steep rising a couple thousand feet from the inlet, and little sunlight reaches the area because of its east-west orientation.
The seven glaciers in the 6-mile-long fjord also keep temperatures low and shorten the growing season.
Other areas have progressed rapidly. At Tlingit Point, in 1916 there were small alder trees. Now the area is covered with large spruce forests.
"It is surprising how quickly the vegetation becomes established after a glacier recedes," Molnia said.
The vegetative growth rate in Glacier Bay far exceeds the growth rate in Interior Alaska due to a warmer climate, abundant moisture and plentiful seed sources.
"This study is part of a big picture understanding of how you can go from a desolate environment to an entire ecosystem," Molnia said. "It is an investigation of how the Earth's surface can respond to changing conditions."
These changes in vegetation have also impacted the wildlife distribution in Glacier Bay.
Preferring dense forests, black bears have moved into the lower regions of the bay, Hazlett said.
Brown bears in the early 1900s were occasionally spotted in the lower bay area, but now inhabit the open upper bay area.
"When early explorers were in the area, they almost never mentioned bear encounters in their journals or field notes," she said. "Now as a result of plant succession creating good habitat for bears, both black bears and brown bears are common in the area."
This summer, the team plans to study vegetative growth in the Kenai Fjords National Park and Prince William Sound.
