Which phenomenon has greatest potential to raise global sea levels?

Which phenomenon has greatest potential to raise global sea levels?

• A. Melting of Antarctic ice shelf
• B. Melting of Greenland's ice sheet
• C. Melting of Arctic sea ice
• D. Melting of Himalayan glaciers

Answer: (B)

When thinking about what raises sea levels, focus on water added to the oceans from land, not ice that’s already floating. Floating ice, like sea ice or ice shelves, doesn’t change sea level when it melts because it was displacing a volume of water equal to its weight anyway. The real impact comes from ice that sits on land and later flows into the ocean. Greenland’s ice sheet is land-based and contains a vast amount of ice. If that ice were to melt completely, it would release a huge volume of water into the oceans, capable of lifting global sea levels by several meters—far more than any of the other options. In contrast, melting Arctic sea ice is from floating ice, so it would not raise sea levels directly. Himalayan glaciers are also land-based, but their total ice mass is much smaller than Greenland’s, so their potential contribution is far less. Antarctic ice shelves are floating; their melt doesn’t by itself raise sea levels, though loss of shelves can accelerate land-ice discharge in the long term. So, the option involving Greenland’s ice sheet has the greatest potential to raise global sea levels.

When thinking about what raises sea levels, focus on water added to the oceans from land, not ice that’s already floating. Floating ice, like sea ice or ice shelves, doesn’t change sea level when it melts because it was displacing a volume of water equal to its weight anyway. The real impact comes from ice that sits on land and later flows into the ocean.

Greenland’s ice sheet is land-based and contains a vast amount of ice. If that ice were to melt completely, it would release a huge volume of water into the oceans, capable of lifting global sea levels by several meters—far more than any of the other options. In contrast, melting Arctic sea ice is from floating ice, so it would not raise sea levels directly. Himalayan glaciers are also land-based, but their total ice mass is much smaller than Greenland’s, so their potential contribution is far less. Antarctic ice shelves are floating; their melt doesn’t by itself raise sea levels, though loss of shelves can accelerate land-ice discharge in the long term.

So, the option involving Greenland’s ice sheet has the greatest potential to raise global sea levels.