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Why Arctic lakes are draining, and how the National Park Service tracks them
Lake surface area in Alaska’s Arctic national parks has significantly declined since the 1980s, and the National Park Service (NPS) says warming temperatures are the cause, with rapid change in the last five years. This resource brief from the Arctic Network explains what is happening, what park scientists want to know and how they find out.
A small lake in Bering Land Bridge National Preserve after large ice wedges near its outlet thawed in June 2018, causing rapid and catastrophic drainage of a Yellow-billed Loon nesting lake. NPS/Jared Hughey
What is happening
The biggest losses are in Bering Land Bridge National Preserve, where many lakes have partly or completely drained. The soil there has a lot of ice-rich permafrost, and when ground ice thaws it widens lake outlets and opens small pathways around the lake, letting the water leak out. Drainage changes the amount of water and can change how much sediment is in the water column and its nutrient, carbon and ion concentrations. It also changes vegetation: plants that like drier conditions, such as trees and shrubs, move in.
Why lakes matter
Shallow lakes and ponds are common across the Arctic. Glaciers, volcanic activity, meandering rivers and thermokarst formed them. Their range of sizes, depths and chemistry makes a mosaic of habitats.
- Furbearers, waterbirds and fish are especially important to Indigenous people, who collect waterfowl and gull eggs, harvest whitefish and salmon, and use small mammal hides for clothing and household items. Wetland plants go into baskets and ornamental objects such as dance fans, and into food and medicine.
- Visitors enjoy the lakes for their beauty and for recreation.
- Lakes and wetlands are often called the “kidneys of the landscape” because they clean water by trapping sediment, nutrients and organic material such as leaves.
What scientists want to know
- How much of the landscape is lake, and is that changing? That shows whether habitat for important fish and wildlife is being lost.
- Is lake chemistry changing? Nutrient, carbon and ion levels indicate whether productivity is changing, whether lakes store or release carbon, and whether erosion patterns are shifting.
- Is vegetation around the lakes changing? That shows whether the food web is changing, and helps explain shifts in animals the network monitors, such as Yellow-billed Loons.
Water-quality sensors track surface temperature, pH, specific conductivity and dissolved oxygen, which indicate habitat quality for the fish and wildlife that use the lakes.
How they monitor
Remote sensing tracks changes in lake surface area across most lakes in the network. Visiting lakes is expensive, so only a few are visited, in two groups:
| Group | What is measured | How often |
|---|---|---|
| Six continuous monitoring lakes | Sondes record hourly temperature, pH, oxygen and salinity | The team tries to visit the same six every year |
| Synoptic monitoring sites | Nutrient, carbon and ion concentrations (Ca, Mg, Na, K), plus temperature, pH, vegetation, depth and size | A couple of times each decade; 337 lakes visited since 2009 |
Sonde locations (blue dots) are monitored hourly during the open-water season; synoptic monitoring sites (red dots) are visited a couple of times each decade. NPS/Dylan Schertz
What the data show
Continuous monitoring began in the late 2000s. Both lake temperature and specific conductance, a measure of salinity, have increased significantly. Temperatures rose with air temperature and, more surprisingly, with wind speed, which could reflect more lake mixing or stronger storms linked to less sea ice in the Bering and Chukchi seas. For the saltier water the page offers two explanations: more sediment entering lakes, from erosion as permafrost thaws or from wind stirring up soil particles, or warmer soil letting runoff soak deeper and pick up minerals on the way to the lake.
Lakes do not all change alike, so the team samples as many as it can. The synoptic data helped identify 10 common types of lake in Alaska’s northern parklands, eight of them found in the Arctic Network. They differ in shape, size, chemistry and bottom sediment, which determines productivity: sandy and gravelly lakes tend to have few plants and animals, while lakes with mineral-rich sediments are more diverse and productive.
Mean annual water temperature and specific conductance have increased significantly in one of the continuous monitoring lakes in Kobuk Valley National Park. Monitoring there began in 2008, was suspended in 2020 because of the COVID-19 pandemic and was due to resume in 2022.
Shallow lakes in the Ahnewetut wetlands of Kobuk Valley National Park. They lie between the greater and less sand dunes and are clear and cool because shallow groundwater feeds them.
Why it matters to managers
Whatever drives the changes, they can strongly affect lake food webs. Warmer temperatures can lower fish habitat quality, alter insect populations and vegetation, and change when ice forms, all of which affect people’s ability to gather plants and animals for subsistence and visitors’ ability to enjoy the landscape. Monitoring helps managers protect habitat by educating visitors, legislators and stakeholders, by acquiring land, or by changing regulations to limit development impacts. The page says the most critical action to protect these lakes is to help cut carbon emissions and slow climate warming.
Sources
- National Park Service, Arctic Network Inventory and Monitoring, Shallow Lakes Resource Brief for the Arctic Network; it cites Swanson (2019) for the decline in lake area; rewritten in hubnx's own words.