Sea-level for Greenland is expected to drop in the coming decades. Why?

Question

Sea-level for Greenland is expected to drop in the coming decades.  Why?

BlackTom AI · Accepted Answer

Isostatic rebound and gravitational attraction together explain why local sea level around Greenland can drop even as global average sea level rises.

1) Relevant concepts
- Glacial isostatic adjustment (GIA): ice sheets depress the crust by their weight; when ice melts, the crust rebounds (uplifts), raising the land relative to the sea.  
- Gravitational and elastic sea‑level fingerprints: large ice masses gravitationally attract nearby ocean water; when an ice sheet loses mass the local gravitational pull weakens and water migrates away from the vicinity, lowering local sea surface height.  
- Global mean sea level (GMSL) vs. regional sea level: GMSL is set by total added water, but redistribution and land motion produce spatial variability.

2) Step‑by‑step reasoning
- Start: Greenland ice sheet exerts weight on the crust and draws ocean water toward itself by gravity.  
- Ice melts: mass is transferred from ice to the ocean. That increases GMSL globally.  
- Simultaneously, two local effects happen near Greenland: (a) the solid Earth beneath Greenland rebounds upward because the ice weight is removed; (b) the reduced ice mass lessens the gravitational attraction, so some ocean water flows away from Greenland.  
- Net local change: land rises and the nearby sea surface falls relative to that land. Thus relative sea level (sea height measured from land) around Greenland can decline even though GMSL rises.

3) Calculations
- No numeric data provided; the logic is qualitative. Quantitatively, model studies compute the sum of uplift and gravitational redistribution to show net regional fall; both contributions are comparable in scale and act in the same direction (lowering relative sea level near Greenland).

4) Why the correct answer is correct
- Both proposed mechanisms are real and operate together: uplift of the land and loss of gravitational pull both reduce local sea level near Greenland.

5) Why other choices are incorrect
- “Because Greenland's land surface will rise…” (option 1) is true but incomplete — it omits the gravitational redistribution effect.  
- “Because less ice mass … will draw less water…” (option 2) is true but incomplete for the same reason.  
- “Neither of the above” is false because both mechanisms do occur.

6) Conclusion
Both of the above is correct; the provided answer ("Both of the above") is confirmed.

Sea-level for Greenland is expected to drop in the coming decades. Why?单项选择题

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这张地图显示的是哪个区域，描绘的是什么过程？

What is represented in this image?

Is the sea-level drop predicted for Greenland likely to be a global phenomena? In other words, would places like Florida and Hawaii also see lower sea levels?

Which of the following would cause sea level to fall (lower)?

During glacial times sea level was lower than today, dropping sea level by ~120 m and causing the California coastline to be shifted west .

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