What is a glacier?

Before we jump into discourse pertaining to prominent glaciers of the eastern Alaska Range, let’s first discuss what a glacier is and why these masses of ice and snow are important.

A glacier is somewhat difficult to define as many attributes of a glacier are still argued over by professionals in the field. A couple of these discrepancies in qualifiers include how it is formed–such as out of recrystallized snow or not–and how large it is. Many professionals also agree that to be considered a glacier the mass must show some type of movement. As with the previous differences, many people disagree about how much movement is necessary and when that movement occurred to qualify a glacier as such. With that said, there is a widened definition that most people, specialists included, agree on. A glacier is:

A mass of ice greater than 1/10th of a square kilometer (25 acres) and more than one year old.

An extensive portion of our team’s experience with glaciers in the U.S. stems from the eastern part of the Alaska Range, where glaciers such as the Black Rapids, Trident, and Gillam provide a very distinct picture and makeup of these masses. Looking at the Gillam Glacier in person (see image below) makes it a much easier concept to understand.

Types of Glaciers

There are two different types of glaciers. The first type of glacier flows outwardly in every direction with no regard for underlying terrain. Oppositely, the second type is confined by terrain to a particular pathway.

Categories of Glaciers

These two different types of glaciers can be further broken down into different categories. The following breakdown outlines the hierarchy of glaciers. At the core of these differences is the size of the mass, but the type of formation can also play a role in classification.

Hierarchy of Glacier Categories

Type 1

Ice Sheet

These are the largest classification of glaciers. To qualify as an Ice Sheet the mass must be over 50,000 kilometers² (10 million acres). There are only two Ice Sheets left on earth, those covering Greenland and Antarctica.

Ice Cap

An Ice Cap falls just underneath an Ice Sheet. An Ice Cap is similarly qualified–flowing outwardly in all directions–but is less than 50,000 kilometers². Although Ice Caps are rare in the modern-day they can still be found in Northeastern Canada, on Baffin Island, and over the Queen Elizabeth Islands.

Type 2

Mountain (Alpine) Glacier

Icefield

An Icefield resembles an Ice Cap in that it flows outward in several directions, but the difference is that with an Icefield the flow is somewhat controlled by terrain. Thus, it does not have the dome-like shape of an Ice Cap. Several Icefields can be found in the Wrangell, St. Elias, and Chugach mountains of Alaska, along with northern British Columbia.

Cirque Glacier

Cirque Glaciers are the most common type of Mountain (Alpine) Glacier. These glaciers are found in basins or amphitheaters near ridge crests. Most have a characteristic round shape, with a width as wide or wider than its length. They tend to average 1 kilometer² (250 acres) in size and are usually less than 100 meters (300 feet) thick.

Valley Glacier

Valley Glaciers are bound by terrain and flow down valleys, bend around corners, and fall over cliff lines. The longest valley glacier in North America is the Bering Glacier. The Bering flows off of the Chugach Mountains in southcentral Alaska. It cuts a 203 kilometer (126 miles) path through the mountains and could be well over 500 meters (1,600 feet) thick in some places.

Many glaciers have tributaries that flow into them. These branched valley glaciers can be very small with one or two unnamed tributaries–such as the branched Unnamed Glacier just northwest of McGinnis Glacier that drains into the Delta River–or they can be huge with several formidable glaciers flowing into one branch. Think Trident and Gillam Glaciers.

If a valley or cirque glacier branch ends abruptly at or near the top of a cliff it is called a hanging glacier. A Hanging Glacier can be extremely dangerous as they frequently drop large ice chunks to the valley floor as the glacier pushes over its cliff.

Additional Glacier Categories

Tidewater Glaciers

If a Valley Glacier flows into the ocean it is categorized as a Tidewater Glacier. There are over 50 Tidewater Glaciers that flow into the Pacific Ocean. One of the most popular places to see a Tidewater Glacier is Glacier Bay National Park. Another fantastic group of Tidewater Glaciers flows from the Chugach Mountains into Prince William Sound in southcentral Alaska.

Piedmont Glacier

A Piedmont Glacier is a Valley Glacier that extends out over a plain and spreads into a lobe-shaped pattern. An example of this is the Malaspina Glacier in southeast Alaska. The Malaspina is over 5,000 kilometers² (1 million acres).

Glacier Remaniê

This type of glacier is reworked or reconstituted out of old glacier material. Glacier Remaniês develop at the base of a slope by ice blocks that accumulate and fuse together after avalanching from an overhead hanging glacier.

Glacieretes

Ice Apron

Ice Aprons are thin sheets of ice that drape a mountainside.

Niche (Pocket) Glacier

Niche, or Pocket, glaciers occupy a small hollow or recess in a slope.

Catchment Glacier

A Catchment glacier is nourished by windblown snow from adjacent snowfields.

Why are glaciers important?

Glaciers are extremely important for a variety of reasons. They directly impact everything from our climate and climate temperature, sea levels, and available drinking water.

Glaciers act as our planet’s air conditioner. The polar ice caps impact weather and climate dynamics, including such things as the jet stream. They also act as indicators of changes to our planet that will be delayed. Glaciers are our most visible form of global warming. As we know, many of our glaciers are retreating. Warmer average temperatures throughout the areas that house these masses continue to eat away at their size and structure. One of the delayed negative side effects associated with this loss deals with sunlight. Glacier’s white surfaces reflect the sun’s rays, which in return provides a cool and mild climate. As glaciers melt, these surfaces become darker (i.e. absorb and release heat), raising the overall temperature.

Melting freshwater from glaciers can also alter the ocean. Beyond raising the global sea level, it also pushes down salt water (water is the only substance that is lighter in its solid-state (ice) than in its liquid state). Water has more density as saltwater than as freshwater. This has a direct impact on things like water currents.

It is important to note the current makeup of the earth. Its surface is currently made up of 71% water, 10% ice, and 19% land. Water expands both when frozen and heated. It is estimated that within our lifetime the sea level will rise by nearly one meter through the melting of ice caps and glaciers along with the thermal expansion of ocean water. Rising sea levels can–and will–adversely affect billions of people in India, Bangladesh, China, and varying parts of the U.S.

When most people think of glaciers they likely picture an image from Glacier Bay National Park & Preserve in southeastern Alaska. This image contains a large commercial boat bustling with tourists, their cameras in hand as it steers closer to a massive tidewater glacier. Yes, glaciers are significant tourist attractions, but they play a much more crucial role in the lives of many. Glaciers are a natural resource, and people from countries all over the world utilize their meltwater.

Those who live in arid, mountain climates often rely on glacial melt for drinking water. In countries such as China, India, and other parts of Asia, snowmelt from the Himalayas feeds many of the rivers. It is the main source of drinking water. Late in the summer, glacial melt takes over this role. In La Paz, Bolivia, people rely heavily on meltwater from a nearby ice cap during long droughts. Glaciers are also used to irrigate crops and generate hydroelectric power, using electricity that is powered by damming the flow of glacial meltwater.

Glaciers And Climate Change

An Interconnected Web

Glaciers are extremely valuable assets in both researching and understanding climate change. Scientists can use ice cores–drilled and extracted from glaciers–to produce long-term climate records. They can use these cores to analyze trapped air bubbles, which paint a picture of past atmospheric composition, temperature variations, and even types of vegetation. Glaciers are able to preserve small amounts of past atmospheric makeup dating back thousands of years within these air bubbles. They can also preserve this information deeper within their core, within the ice itself. Scientists can use this data to reconstruct past eras, and through this show how and why the climate changed. This information can then be used to try and determine future climate composition and how it might change with evolving trends.

We understand that glaciers are masses of ice and that these masses are extremely sensitive to temperature fluctuations. With this, scientists can use observations in glacial change due to temperature swings to answer questions about global warming. Since the early 1900s, many glaciers around the world have been in constant retreat (i.e. melting away rather than growing larger). Many argue that this ‘great retreat’ has a direct correlation with the Industrial Revolution (circa 1760). A strong argument for this narrative is that throughout the twentieth century several ice caps and ice shelves have disappeared completely. Many that haven’t vanished altogether lay on the cusp of doing so.

There is no doubt that human activity plays a significant role in the disappearance of glaciers. The production of electricity using coal and petroleum, along with additional fossil fuel use, directly affects our environment. Throughout the past 200 years, human activity has increased the amount of carbon dioxide in the atmosphere by 40 percent. With other gases, like methane, it's a factor of 2 to 3 (or more). These gases obtain heat being radiated from the surface of the earth and through the absorption of this heat the atmosphere begins to warm up. Greenhouse gases are the cause of the majority of climate warming, and in direct relation to this, glacial retreat. Other causes play a role in glacial retreat as well, including an increase in dust and soot from commercial businesses like farming.

One glacier tells a short story, but a collection of glaciers can create a book. Through the tracking of many glaciers, worldwide scientists can better learn about, understand, and tell the story of the global climate. The World Glacier Monitoring Service (WGMS) tracks the changes of more than 100 mountain glaciers. This holistic approach to glacier surveying provides some of the most prominent data regarding global climate and climate change.

Environment And Location

Eastern Alaska Range

Moving forward, we will be discussing the aforementioned relationship between glaciers and habitats, people, and climate on a more localized level. We will take these concepts and apply them directly to the eastern Alaska Range and the state’s interior. Let’s begin by quickly discussing where this environment is located.

The Alaska Range sits in southcentral Alaska and stretches 400-miles from Lake Clark at its southwest to the White River in Canada’s Yukon Territory at its southeast. The eastern Alaska Range is a subsection of the Alaska Range. One might find it a headache to try and divide such a vast environment into separate sections, but in actuality, the separation is fairly straightforward.

So, where does it split away from its sister peaks? The George Parks Highway (known more generally as the Parks Highway) creates the border between these two ranges. Skyscraping, snow-capped peaks are contrasted by flat and barren tundra, and wildlife can be seen at all spots along the way from Anchorage to Fairbanks.

The peaks throughout the eastern part of this range see very little attention due to their higher neighbors to the west. Given that Denali (formerly Mt. McKinley) is the tallest peak in North America, it is the centerpiece of the Alaska Range. Denali’s close relatives, Mount Foraker, Mount Hunter, and Mount Huntington, also steal much of the limelight away from the prominent peaks of the eastern Alaska Range. The eastern Alaska Range sits just south of Fairbanks. On a clear day, one can see all of the major peaks of the eastern Alaska Range from the city itself.