The Earth's oceans are rising. It's an inevitable outcome when ice sitting on land melts and when oceans warm, which causes their volume to expand. But if you live at the coast, it may not be rising near you. Places like Miami and Newport News are experiencing floods at many high tides. Some places in Alaska, in contrast, are seeing the oceans edging away, as land seems to lift out of the sea (albeit incredibly gradually).

How can that happen?

It happens because the Earth's not a bathtub—adding more water doesn't increase ocean levels evenly. As this video details, there are lots of factors that add a local twist to the overall rise of the oceans. These factors range from the strength of ocean currents to the gravitational pull of large ice fields. The net result is that the US has some areas where ocean levels are actually falling a bit and many others where they're rising even faster than the global average.

While the effects are small, they can make a huge practical difference, determining whether your neighborhood is flooding now, or if you have decades to prepare for problems.