D4.3.4 Melting of landfast ice and sea ice as examples of polar habitat change Notes

Melting of Landfast Ice and Sea Ice as Examples of Polar Habitat Change

1. Polar regions are undergoing rapid environmental changes due to climate change, with melting landfast ice and sea ice posing serious threats to ecosystems.
2. These icy habitats serve as critical breeding and hunting grounds for many species, and their loss disrupts entire food chains.
3. Two key examples of this phenomenon include:
   1. The loss of landfast ice in Antarctica, threatening the breeding grounds of the emperor penguin (Aptenodytes forsteri).
   2. The loss of Arctic sea ice, endangering walrus populations, which rely on ice floes for resting and foraging.

Landfast Ice vs. Sea Ice: What's the Difference?

1. Landfast ice provides stable platforms for breeding, while sea ice serves as hunting and resting grounds.
2. Unlike landfast ice, sea ice moves with ocean currents. It is crucial for species such as walruses, polar bears, and seals, which depend on it for survival.

Emperor Penguins (Aptenodytes forsteri) and the Loss of Landfast Ice in Antarctica

1. Emperor penguins depend on landfast ice for their breeding colonies.
2. Traditionally, they lay their eggs and raise their chicks on stable ice platforms from May to December.
3. However, due to early ice breakup, entire colonies may be destroyed, as chicks may not have fully developed waterproof feathers before being forced into the water.

Why Is This Important?

Emperor penguins are an indicator species and their decline signals broader ecological disruptions in the Antarctic.

Loss of Sea Ice Habitat for Walruses in the Arctic

1. Walruses (Odobenus rosmarus) are large marine mammals that rely on sea ice for several aspects of their life cycle.
2. They use the ice as haul-out sites (places to rest and socialize) and as platforms to access the water for feeding.

How Melting Sea Ice Affects Walruses

1. As the sea ice melts earlier and retreats further north, walruses are forced to haul out on land or other unstable platforms, increasing their vulnerability to predators (like polar bears) and making it harder for them to access their feeding grounds.
2. The melting of sea ice also limits the habitat available for walruses to rest and socialize. This can increase stress levels in populations, making it more difficult for individuals to maintain health and reproductive success.

Key Factors Contributing to Ice Loss

Rising Global Temperatures

1. The global warming trend caused by increased greenhouse gas emissions is leading to higher air and ocean temperatures, particularly in the polar regions.
2. These higher temperatures accelerate the melting of both landfast ice and sea ice.

Feedback Loops

1. Melting ice exposes more open water, which absorbs more sunlight, leading to further warming.
2. This positive feedback loop accelerates the process of ice melt, making the polar regions more vulnerable to temperature increases.

Changes in Ice Thickness

As the ice continues to thin, it becomes less stable and more prone to breaking apart or melting completely during warmer seasons, further disrupting the habitats of species dependent on these ice platforms.