Final answer:
The observation that the arctic sea ice has declined by 1.57 square kilometers since 1979 is a quantitative observation supported by scientific research and data.
Step-by-step explanation:
The given observation, which states that the arctic sea ice has declined by 1.57 square kilometers since 1979, is a quantitative observation. The reason for this is that it provides a specific numeric value (1.57 square kilometers) as evidence of the decline in the Arctic sea ice. This is in contrast to a qualitative observation, which would describe the decline without providing a specific measure.
The decline in arctic sea ice is backed by scientific research and data, which shows that the extent of sea ice has been decreasing over time. The decrease in sea ice has numerous implications, including impacts on global climate, ecosystems, and sea level rise.