An Insight Into Ice

Glaciers are a magnificent part of the landscape of Kenai Fjords National Park. They are responsible for carving the park's fjords, they nourish downstream ecosystems, and they provide recreational opportunities for visitors to the park. Although glaciers may appear to be permanent, unchanging features — things that change very slowly are often said to move at "a glacial pace" — glaciers are actually quite dynamic, changing in size in response to changes in their environment. How do we know that glaciers are changing in size? One method is to use photographs, taken by people on the ground or from satellites in space. By comparing photographs of the same location from different dates (repeat photography), we can monitor how glaciers change over time.

A glacier is an ice feature formed by the accumulation and compaction of snow — so much of it that it deforms under its own weight and flows downhill. How do glaciers grow and shrink? We can think of this like a bank account. Over time, snow on a glacier transforms into ice, like making a deposit into a bank account. When temperatures rise above freezing, the glacier melts, like making a withdrawal. If the glacier gains more snow than it loses to melt each year (if you earn more money than you spend), the glacier will grow. But, if the glacier melts more than it gains in new snow and ice each year (if you spend more money than you earn), it will shrink. These changes in size add up over time, and can be measured in many different ways, including repeat photography.

Most glaciers in Kenai Fjords National Park are on or near the coastline. For each coastal glacier in this story, there is a comparison of repeat photographs, a map of glacier outlines as measured from satellite images, and a chart showing how the length of the glacier changed. In each map, the white outlines show older glacier extents, from 1984, while dark orange outlines show newer glacier extents, from 2021. Scroll through the whole story, or use the headers at the top to navigate to individual glaciers. The glaciers are organized by the environment where the end of the glacier, or terminus, is located, because glaciers have different effects on different types of environments, and different environments can also have different effects on a glacier.

Lake-terminating glaciers are those that terminate, or have their ends located in, a lake. In Kenai Fjords National Park, coastal glaciers that are lake-terminating include Bear, Pedersen, and Yalik Glaciers. Petrof Glacier was also lake-terminating from at least 1984 until 2006. Lake-terminating glaciers influence the ecosystems and physical properties of the freshwater lakes that they reach into, as well as of streams flowing out of the lakes. Lake-terminating glaciers make their freshwater lakes colder, and they increase turbidity, or cloudiness of the water caused by tiny particles of glacier-scoured rock suspended in the water. These effects can make it harder for some varieties of life to survive in the lake. However, as these glaciers retreat, their lakes grow, and this can create new habitat for animals like sockeye salmon. The lakes in front of lake-terminating glaciers are also popular recreational areas, especially at Bear Glacier, where park visitors travel to kayak and paddleboard on the iceberg-filled lake and camp on its shores.

Land-terminating glaciers are those that terminate on land, so that the entire glacier sits on land. Land-terminating coastal glaciers in Kenai Fjords National Park include Northeastern, Southwestern, Sunlight, Paguna, Dinglestadt, and Split Glaciers. Land-terminating glaciers influence habitats on land and in rivers adjacent to the glaciers. In Kenai Fjords, these rivers also flow directly into the ocean, where they deliver sediments and nutrients and influence temperatures. As many of these glaciers retreat, forests and river systems develop in their wake, creating new habitats. The newly formed forests and rivers go through a process of colonization called succession in which biological communities develop and create new ecosystems. However, in advanced stages of glacier retreat, changes in the amount of water flow, temperature, and sediment load can result in additional adjustments to the ecology of the adjacent water body. The retreat of land-terminating glaciers can open up new recreational opportunities in Kenai Fjords National Park, as the recently deglaciated landscapes may offer flatter terrain and more easily-followed routes through the surrounding forest.

Tidewater glaciers are those that terminate in marine environments, like the seawater fjords of Kenai Fjords National Park. Current tidewater glaciers in the park include Aialik, Holgate, Northwestern, Ogive, Anchor and McCarty Glaciers, while recently-tidewater glaciers (which have retreated and become land-terminating) include South Holgate and Reconstitution Glaciers. Tidewater glaciers influence the physical properties and ecosystems of marine environments. Glacial meltwater and glacially-scoured rock sediment affect the temperature and turbidity (cloudiness) of the water in glaciated fjords. Changes to temperature and turbidity influence different nutrients in the water, and consequently the abundance of prey and predator animals. Tidewater glacier melting and iceberg calving affect the circulation of water near the glacier, which also influences the distribution of nutrients near the glacier. The tidewater glacier environment also provides habitat for a variety of species; for instance, harbor seals haul out on icebergs that break off of tidewater glaciers.

While all glaciers are sensitive to changes in climate, the behavior of tidewater glaciers can be affected by some additional factors through what is known as the tidewater glacier cycle. In this cycle, a glacier starts at an advanced position. A change in local conditions, like warming temperatures, causes the glacier to start retreating. The glacier's retreat is strongly affected by factors like the depth and width of the fjord that it is in. Eventually the glacier stabilizes in a new retreated position. The glacier may then start to build a protective sediment shoal in front of it, allowing it to slowly advance again. These cycles can occur at different times at different glaciers; however, currently most tidewater glaciers in Alaska and elsewhere in the world are retreating.

The coastal boundary of Kenai Fjords National Park is defined as the location of "mean high tide". So, when a tidewater glacier in the park advances or retreats, the park boundary moves with the location where the ice meets the ocean. This means that when a tidewater glacier retreats, the park loses acreage. In the future, when the park's tidewater glaciers have retreated entirely onto land, the park's boundary will become more static.

Repeat photography and satellite measurements show that most glaciers in Kenai Fjords National Park have lost ice. During the period of satellite measurements, from 1984 to 2021, only two glaciers grew larger (Holgate Glacier and Paguna Glacier). Climate change predictions show that glacier ice in this region will continue to melt. The loss of ice from these glaciers has and will continue to affect lake, land, and marine environments as water bodies grow and vegetation cover changes. These changes can be both beneficial and detrimental to local ecosystems, as some species gain habitat while others lose it. Recreational opportunities will also change: more land and water will become available for recreation, but glacier retreat will also affect the views and wildlife that the park is known for.