[Physics] Why do sea levels not rise uniformly around the world

fluid dynamicsfluid-staticsgeophysicsoceanography

While reading the article Hawaii’s Beaches Are in Retreat, and Its Way of Life May Follow on The New York Times's website, I was surprised to find out that sea levels do not rise around the world at a uniform rate. Assuming that the global warming is true (I think there's enough credible evidence for it – but I don't want a debate on the veracity of global warming – therefore, just assume it's true), what may be the reason for the non-uniformity?

Best Answer

There's a good article about this at http://climate.nasa.gov/blogs/index.cfm?FuseAction=ShowBlog&NewsID=239. Since it's a NASA blog I assume it's reasonably trustworthy. The key points are:

  • ocean currents and the prevailing wind patterns cause water build ups in some areas
  • ocean temperatures vary and higher temperature areas have higher levels because the water density is lower
  • the weight of ice sheets affect the Earth's axis of rotation and the water distribution

I must admit I'm not sure about the last of these as it seems to me it would be a very small effect. Finally, another longer term effect I've seen mentioned in some discussions is that land rises as it's freed from the weight of the ice. The north of the UK is still rising, and the south still sinking, after the ice melted at the end of the last ice age.