Sea level isn't really level at all

Our friends at NASA’s Global Climate Change site have a great blog post today that we’d like to share. The message is simple yet critical: rising sea levels do not and will not mean the same thing everywhere on the planet. Oceanographer Josh Willis of the Jet Propulsion Laboratory puts it this way:

Even though it’s sometimes convenient to think of the ocean as a great big bathtub, where turning on the tap at one end raises the water level in the whole tub, real sea level rise doesn’t quite happen that way. To understand why, you first have to realize that ‘sea level’ isn’t really level at all.

There are lots of reasons why the oceans are not level. For example, vast ocean currents like the Gulf Stream in the Atlantic Ocean and the Kuroshio in the Pacific actually reshape the ocean surface, causing it to tilt. As the planet heats up, changes in the prevailing winds (which drive most of these ocean currents) cause changes in the currents, reshaping our ocean and changing local sea level as a result.

Just as global warming does not raise land temperatures evenly, global ocean warming is not the same everywhere around the globe. Some regions of the oceans are heating up faster than others, and because warm water takes up more space than cold water, those regions experience faster sea level rise.

Finally, the water locked away in the great ice sheets of Greenland and Antarctica also shapes the ocean surface. As the ice sheets melt and lose water to the oceans, our entire planet feels the effects. The movement of mass from the ice sheets to the oceans very slightly shifts the direction of Earth’s rotation. This, along with changes in the gravitational pull of the ice sheets on the oceans, will reshape sea levels further still…

Click here to read the full posting from Josh. And be sure to check out the interactive sea level rise viewer. 

— Mike Carlowicz, Earth Science News Team

3 thoughts on “Sea level isn't really level at all”

  1. While your points are well taken, there are other reasons that the seas are never “level” if it were. The earth itself isn’t perfectly spherical and as such it tends to bulge in a non-uniform fashion. This results in regional gravitational deformities and non-level seas. I think the important aspect of your article is that the oceans are complex systems which are not easily characterized by simple formulas.

  2. It's really great and fantastic blog. Information are so helpful.Thanks for sharing such a informative post with us. Keep blogging.

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