Why is sea level rising?
So on global scales, sea level is rising really because of our warming climate.
There’s two main factors causing sea level to change.
The first is what we call thermal expansion. So as more heat gets trapped by the atmosphere, a lot of that heat gets absorbed by the ocean. When water warms, it actually expands and that causes sea level to go up.
The other reason that sea level is rising is because of melting ice. So we have a lot of ice contained in the ice sheets, the Antarctic, Greenland ice sheets and different mountain regions. As the Earth warms, these regions are also warming.
So what happens is this ice melts, and when it melts, that meltwater flows into the ocean. So again, this causes sea level to go up.
Global sea levels are rising as a result of human-caused global warming, with recent rates being unprecedented over the past 2,500-plus years. NASA JPL’s sea level rise expert Ben Hamlington explains how our warming planet is causing sea levels to rise. Credit: NASA
On regional scales, the rates of sea level rise can actually be quite different. The ocean doesn’t fill like a bathtub. Different parts of the ocean see more of an effect than others, depending on two main factors.
The first of these is something we call ocean dynamics. So as the climate changes, there can be changes in our ocean circulation, the currents, and this actually changes how water is distributed and moved about the Earth, causing sea level to be different in some locations than others.
The other reason that we see differences in the rates from one region to the next is something we call the ice sheet fingerprints. So there’s so much ice being lost from these different locations, from the ice sheets that it actually affects the gravity and rotation of the Earth.
And we have these distinct, what we call fingerprints, that really dictate where the water goes when it melts.
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