Home · The year-wheel desk
Arctic and alpine
A year-wheel that keeps the two kinds apart
Temperature, thaw and the length of the growing season belong on the same desk, as long as Arctic figures are not asked to describe a Colorado ridge, or the other way around.
Choose a topic. The comparison table below stays put. It is the same set of published figures, seen together, not a different record.
The year-wheel
For Arctic tundra, the Park Service says the growing season ranges from just 50 to 60 days. [NPS Arctic] For alpine tundra, the same Park Service page says the growing season is approximately 180 days. [NPS Arctic] July is generally the warmest month on the park’s tundra, with an average high temperature of 52°F (11°C). [NPS Rocky Mountain] Summer on the tundra is short; snow is prominent on the landscape into June, with a few isolated snow patches remaining through the summer. [NPS Rocky Mountain] Tundra wildflowers in the park bloom from late May through early August. [NPS Rocky Mountain] During summer months, the top layer of soil thaws — known as the active layer — creating a wet landscape with rapid runoff. [NPS Arctic]
The wheel is a way of seeing those figures together. It is not a third source, and it does not invent Arctic start and end dates that the Park Service did not publish.
The year-wheel
For Arctic tundra, the Park Service says the growing season ranges from just 50 to 60 days. [NPS Arctic] For alpine tundra, the same Park Service page says the growing season is approximately 180 days. [NPS Arctic] July is generally the warmest month on the park’s tundra, with an average high temperature of 52°F (11°C). [NPS Rocky Mountain] Summer on the tundra is short; snow is prominent on the landscape into June, with a few isolated snow patches remaining through the summer. [NPS Rocky Mountain] Tundra wildflowers in the park bloom from late May through early August. [NPS Rocky Mountain] During summer months, the top layer of soil thaws — known as the active layer — creating a wet landscape with rapid runoff. [NPS Arctic]
The wheel is a way of seeing those figures together. It is not a third source, and it does not invent Arctic start and end dates that the Park Service did not publish.
Two kinds of tundra
The National Park Service says tundra is the coldest of biomes, and that the name comes from the Finnish word tunturia, meaning treeless plain. [NPS Arctic] There are two types of tundra, the same page says: arctic tundra is above latitudinal treeline and alpine tundra is above elevational treeline. [NPS Arctic] The mountains of the Brooks Range have both kinds of tundra. [NPS Arctic] Rocky Mountain National Park also says that, across the globe, there are two types of tundra — alpine and arctic — and that alpine tundra, the type found in the park, occurs at high elevations where temperatures are colder, winters are longer, and growing seasons are shorter. [NPS Rocky Mountain]
Treeless, cold, and relatively dry, in two settings: far north, and high up. The Brooks Range is one place where both occur.
The Arctic year
For Arctic tundra, the Park Service says the growing season ranges from just 50 to 60 days. [NPS Arctic] Arctic tundra is underlain by a layer of permanently frozen soil called permafrost, which is permanently frozen ground that affects nearly everything in the Arctic ecosystem, including soils, vegetation, water, and wildlife. [NPS Arctic] During summer months, the top layer of soil thaws — known as the active layer — creating a wet landscape with rapid runoff. [NPS Arctic] Arctic tundra, as high-latitude tundra, is located in the northern hemisphere, encircling the north pole and extending south to the coniferous forests of the taiga or boreal forest, and the Arctic is known for its cold, desert-like conditions. [NPS Arctic]
A short growing season, permafrost underneath, and a summer thaw that wets the surface. That is the Arctic ring on the wheel.
The alpine year
For alpine tundra, the same Park Service page says the growing season is approximately 180 days. [NPS Arctic] RMNP’s tundra starts between 11,000 and 11,500 feet, a transition zone, or ecotone, where the forested subalpine zone shifts to the treeless tundra and is often referred to as treeline. [NPS Rocky Mountain] Summer on the tundra is short; snow is prominent on the landscape into June, with a few isolated snow patches remaining through the summer. [NPS Rocky Mountain] July is generally the warmest month on the park’s tundra, with an average high temperature of 52°F (11°C). [NPS Rocky Mountain] Tundra wildflowers in the park bloom from late May through early August. [NPS Rocky Mountain]
The 180-day growing season is a general alpine figure. The snow, flower and July-temperature dates are from Rocky Mountain National Park, and they stay labelled as such.
Permafrost, kept labelled
Arctic tundra is underlain by a layer of permanently frozen soil called permafrost, which is permanently frozen ground that affects nearly everything in the Arctic ecosystem, including soils, vegetation, water, and wildlife. [NPS Arctic] Alpine tundra is distinguished from Arctic tundra, that page says, in that alpine tundra typically does not have permafrost and alpine soils are generally more porous than Arctic soils. [NPS Arctic] Permafrost, which the park defines as an area with a permanently (year-round) frozen subsurface soil layer, is common and widespread in arctic tundra, but patchier within alpine tundra. [NPS Rocky Mountain]
Widespread under Arctic tundra, on both pages. For alpine tundra, one page says typically none, and the other says patchier. The desk keeps both.
Different lines on the map
There are two types of tundra, the same page says: arctic tundra is above latitudinal treeline and alpine tundra is above elevational treeline. [NPS Arctic] Lake Clark National Park and Preserve says there are two kinds of tundra in Alaska, alpine and arctic: Arctic tundra is found north of the permafrost line, generally north of the arctic circle, and alpine tundra is found around the state at high elevations — the kind found in that park. [NPS Lake Clark] The National Natural Landmarks tundra page says alpine tundra are found at high elevation on mountaintops, whereas arctic tundra are located on high-latitude landmasses above the Arctic Circle or in far southern reaches like Antarctica. [NPS landmarks]
Latitudinal treeline, the Arctic Circle, and “north of the permafrost line” are related, and they are not the same boundary. Antarctica appears on the landmarks page as a far-southern counterpart, not as a third kind of tundra.
Swipe to see the whole table.
| Topic | Published figure | How to read it |
|---|---|---|
| Growing season, Arctic tundra (NPS Arctic) | 50 to 60 days | A length, not a calendar of start and end dates. |
| Growing season, alpine tundra (NPS Arctic) | Approximately 180 days | A general alpine figure, not the Rocky Mountain flowering dates on the same desk. |
| Where each kind sits (NPS Arctic) | Arctic: above latitudinal treeline. Alpine: above elevational treeline. | The Brooks Range has both. Latitude and altitude are not the same line. |
| Another Arctic wording (NPS Lake Clark; NPS landmarks) | North of the permafrost line, generally north of the Arctic Circle; or high-latitude landmasses above the Arctic Circle, and far southern reaches such as Antarctica. | These are not identical to “latitudinal treeline.” They stay labelled. |
| Permafrost, Arctic (NPS Arctic; NPS Rocky Mountain) | Underlain by permafrost; common and widespread in arctic tundra. | Two Park Service pages, in agreement on the Arctic. |
| Permafrost, alpine (NPS Arctic; NPS Rocky Mountain) | Typically does not have permafrost (Arctic-overview page); patchier within alpine tundra (Rocky Mountain). | Both wordings stay on the desk. They are not combined into a single rule. |
| A Rocky Mountain summer (NPS Rocky Mountain) | Snow prominent into June; flowers late May to early August; July average high 52°F (11°C). | Park-specific alpine dates, not an Arctic calendar. |
Checked on 15 November 2026. The desk does not average a 50-to-60-day Arctic season with a 180-day alpine one, or tidy two permafrost wordings into a single sentence.