why do glaciers move during storms?

The Deep Dive

Glaciers, immense rivers of ice, are constantly in motion, but their movement isn't a steady, uniform creep. During storms, especially those involving heavy snowfall or rain, a fascinating phenomenon occurs that can accelerate glacial flow. The primary mechanism is basal sliding, a process where the glacier slides over the bedrock beneath it. This sliding is facilitated by a thin layer of meltwater that forms at the glacier's base. Increased precipitation from storms can lead to more water at the base in two ways: firstly, heavy snowfall insulates the ice, trapping geothermal heat and promoting melting from below. Secondly, if the storm involves rain, it can percolate through the ice or flow over the surface, eventually reaching the base and increasing the meltwater layer. This water acts as a lubricant, significantly reducing the friction between the ice and the bedrock. Furthermore, the immense weight of the glacier, which can be thousands of feet thick, exerts enormous pressure on this basal layer. This pressure lowers the melting point of ice, contributing to the formation of meltwater even at sub-zero temperatures, a process known as pressure melting. When storms enhance the meltwater supply, this lubricating layer becomes more effective, allowing the glacier to slide more readily, leading to a noticeable increase in its velocity.

Why It Matters

Understanding glacial movement during storms is crucial for predicting how glaciers respond to changing climate patterns. Accelerated glacial flow can directly impact sea-level rise projections, as faster-moving glaciers deliver more ice to the ocean. This knowledge also helps in assessing risks associated with glacial lakes and outburst floods, which can be triggered by rapid glacial changes. For communities living downstream from glaciers, monitoring these movements is vital for hazard preparedness and water resource management, as glacial melt is a significant source of freshwater in many regions.

Common Misconceptions

A common misconception is that glaciers only move through a slow, internal deformation, like very thick toothpaste. While internal deformation does occur, especially in the upper layers of the ice, basal sliding is a far more significant contributor to overall glacial movement, particularly in warmer glaciers. Another myth is that glaciers are static, frozen entities. In reality, all glaciers are dynamic and continuously flowing, with their speed varying greatly depending on factors like temperature, slope, and the presence of meltwater at their base, which is often enhanced during stormy weather. Storms don't 'push' glaciers, but rather create conditions that enable them to slide more easily.

Fun Facts

• Glaciers can move anywhere from a few centimeters to several meters per day, with storm-enhanced periods potentially seeing even faster speeds.
• The largest glaciers can weigh trillions of tons, exerting immense pressure on the bedrock beneath them.