Final Answer:
The observations about changes in Arctic sea ice since 1979 include:
- a) Decreased sea ice extent
- c) Changes in ice composition
- d) Polar bear population decline
Step-by-step explanation:
Since 1979, observations in the Arctic indicate decreased sea ice extent, not increased thickness, alongside potential changes in ice composition, and these alterations have influenced the declining polar bear population.
Since 1979, there has been a consistent and significant decrease in Arctic sea ice extent, particularly during summer months. However, there hasn't been a notable increase in sea ice thickness; instead, thickness has generally declined due to a shift toward younger, thinner ice. Additionally, there are indications of changes in ice composition, such as the ratio of multi-year ice to seasonal ice.
These alterations in the Arctic environment have had profound effects on the habitat and hunting grounds of polar bears, contributing to their population decline. The reduction in sea ice limits their access to prey, impacts breeding habitats, and heightens challenges for survival.
Correct answer:
- a) Decreased sea ice extent,
- c) Changes in ice composition,
- d) Polar bear population decline.