Yes, glaciers can indeed grow back, demonstrating their dynamic and responsive nature to specific environmental conditions.
The Dynamic Nature of Glaciers
Glaciers are not static blocks of ice; they are complex, dynamic systems constantly gaining and losing mass. Their "health" is determined by a balance between accumulation (snowfall and ice formation) and ablation (melting, sublimation, and calving). A glacier grows or advances when accumulation exceeds ablation, leading to an overall gain in ice volume and extent. Conversely, it shrinks or retreats when ablation outpaces accumulation.
A Notable Example: Greenland's Jakobshavn Glacier
A compelling and recent example of glacial growth comes from Greenland. The Jakobshavn glacier, which was previously known as one of Earth's fastest-shrinking ice masses, has begun growing again. A new NASA study, findings of which were reported on March 25, 2019, confirmed this remarkable reversal.
- Previous State: Around 2012, the Jakobshavn glacier was experiencing rapid shrinkage, retreating approximately 1.8 miles and thinning nearly 130 feet annually.
- Current State: The NASA study revealed that the glacier is now growing again. This unexpected turn is largely attributed to a regional cooling of ocean waters, which has reduced the rate of ice melt at the glacier's front.
This turnaround for Jakobshavn highlights that while global warming causes widespread glacial retreat, regional and localized factors, such as shifts in ocean currents and temperatures, can significantly influence the behavior of individual glaciers.
Factors Contributing to Glacial Growth
Several factors can contribute to a glacier's ability to grow or regain mass:
- Increased Snowfall: Higher precipitation, particularly in the form of snow, directly adds mass to the glacier's accumulation zone. This additional snow compacts over time, turning into ice and contributing to the glacier's overall volume.
- Lower Temperatures: Colder air temperatures reduce surface melting and slow down the rate of ablation. Prolonged periods of colder temperatures can allow a glacier to retain more of its accumulated snow and ice.
- Oceanic Conditions: For tidewater or marine-terminating glaciers (those that flow into the ocean), changes in ocean temperature and currents are critical. As seen with the Jakobshavn glacier, cooler ocean currents at the glacier's front can significantly reduce underwater melting and calving, thereby promoting growth.
- Reduced Calving: If the rate at which icebergs break off from the glacier's terminus decreases, the glacier retains more mass. This can be influenced by factors like water temperature, glacier speed, and the presence of ice mélange.
Implications for Glacial Health
While the growth of specific glaciers like Jakobshavn offers a glimmer of hope and vital insights into glacial dynamics, it's essential to understand that such localized growth does not necessarily counteract the global trend of glacial retreat driven by climate change. However, it underscores the complex interplay of atmospheric, oceanic, and glaciological processes that govern glacier behavior. Understanding these dynamics is crucial for predicting future changes in ice sheets and sea levels.
Here's a comparison of Jakobshavn's condition:
| Period | Glacial Activity | Annual Change (Approx.) | Primary Influence |
|---|---|---|---|
| Around 2012 | Retreating | 1.8 miles retreat, 130 feet thinning | Warmer ocean currents |
| Post-2012 (as of 2019) | Growing | Reversing previous trends | Cooler ocean currents |
