Dynamic alpine glacier with meltwater streams.

Alpine Glaciers: Unveiling the Secrets of Ice Velocity

Author's portrait.
Reese Marlowe in Climate & Environment May 2025 • 4 min read.

"Discover how seasonal changes and water flow dramatically influence the movement of small glaciers, challenging traditional assumptions."


Cirques, those bowl-shaped hollows carved into mountainsides, are more than just visually striking features of glaciated landscapes. They are dynamic environments where glaciers actively sculpt the earth, both by direct erosion and by removing the debris of weathering. Understanding these processes is crucial, especially as we witness the ongoing changes in our warming world.

For decades, a simplified view of cirque glaciers prevailed, depicting them as nearly rigid bodies rotating with minimal internal deformation. This model, while convenient, falls short of capturing the true complexity of these icy formations. At West Washmawapta Glacier in the Canadian Rockies, observations reveal a far more nuanced reality, one where ice dynamics play a pivotal role.

This article delves into the fascinating world of alpine glacier movement, challenging long-held assumptions and shedding light on the intricate interplay between ice, water, and the landscape they shape. Join us as we explore the groundbreaking research that uncovers the secrets of ice velocity in these dynamic environments.

The Rhythmic Pulse of a Glacier: Seasonal Velocity Swings

Dynamic alpine glacier with meltwater streams.

Temperate valley glaciers, extensively studied for their seasonal behavior, exhibit a predictable pattern. During winter, subglacial cavities are small or absent, forming a weakly connected network. As the melt season begins, meltwater and rain reach the bed, increasing water volume and pressure, leading to a period of enhanced basal slip that can last for weeks or months.

Short-term pulses of meltwater input can trigger rapid basal slip, known as 'motion events,' where the glacier's surface speed can increase several times above the background level. These events can cause vertical motion and changes in surface elevation. Later in the melt season, the subglacial drainage network evolves into a high-efficiency channel system, reducing water pressure and volume, causing the glacier to slow down.

  • Spring Speed-Ups: Enhanced water input leads to increased basal slip.
  • Channel Evolution: Efficient drainage reduces water pressure, slowing the glacier.
  • Motion Events: Pulses of meltwater cause rapid, short-term increases in speed.
  • Seasonal Shifts: Transition from inefficient to efficient drainage systems.
At West Washmawapta Glacier, GPS measurements captured surface speed anomalies over three summers. The data revealed that the glacier's movement was far from constant. In one particular year, four distinct motion events were recorded. These events coincided with periods of increased water input to the glacier bed, triggered by either warm weather and rapid melt or intense rainfall. These influxes of water likely enhanced basal water volume and pressure, lubricating the glacier's base and causing it to speed up.

Redefining Cirque Glaciers: A Call for Dynamic Understanding

The observations at West Washmawapta Glacier challenge the conventional view of cirque glaciers as simple, rigidly rotating bodies. The findings underscore the importance of considering the dynamic interplay between ice, water, and the landscape in understanding cirque formation. As we continue to study these fascinating environments, a more nuanced approach is needed, one that recognizes the complex processes at play and their implications for glacial erosion and landscape evolution.

Everything You Need To Know

1

What are cirques and why are they important in understanding glaciers?

Cirques are bowl-shaped hollows carved into mountainsides by glaciers. They are important because they are dynamic environments where glaciers actively sculpt the earth, both by direct erosion and by removing the debris of weathering. Understanding cirques is crucial, especially as we witness the ongoing changes in our warming world. They are not just static features but active zones of glacial activity.

2

What is 'basal slip' and why is it significant for glacier movement?

Basal slip refers to the movement of a glacier along its base, where it interfaces with the underlying bedrock. It's significant because enhanced basal slip is often caused by increased water input, leading to increased water volume and pressure. This increased pressure lubricates the glacier's base, causing it to speed up. It is a key factor in understanding glacial dynamics and its response to environmental changes.

3

What are 'motion events' in the context of glacier movement?

Motion events are short-term pulses of meltwater input that trigger rapid basal slip, causing a glacier's surface speed to increase significantly above the background level. These events can lead to vertical motion and changes in surface elevation. Understanding motion events is important for comprehending the short-term variability in glacier movement and its impact on the surrounding landscape. They demonstrate that glacier movement isn't constant but can rapidly change in response to environmental factors.

4

How do seasonal changes affect the speed of temperate valley glaciers?

Temperate valley glaciers exhibit a predictable seasonal behavior. During winter, subglacial cavities are small or absent. As the melt season begins, meltwater and rain reach the bed, increasing water volume and pressure, which leads to a period of enhanced basal slip. Later, the subglacial drainage network evolves into a high-efficiency channel system, reducing water pressure and volume, causing the glacier to slow down. Understanding seasonal changes is crucial for predicting how glaciers respond to climate variations.

5

What is the significance of the West Washmawapta Glacier in our understanding of glacial dynamics?

The West Washmawapta Glacier is a cirque glacier in the Canadian Rockies where observations have revealed that the glacier's movement is far from constant. Data collected there showed that motion events coincided with periods of increased water input to the glacier bed, triggered by either warm weather, rapid melt or intense rainfall. The study of West Washmawapta Glacier challenges the conventional view of cirque glaciers as simple, rigidly rotating bodies, underscoring the dynamic interplay between ice, water, and the landscape.

Newsletter Subscribe

Subscribe to get the latest articles and insights directly in your inbox.