If you follow news articles about changing climate, you have no doubt seen many stories about melting sea ice, glaciers, and the big ice sheets in Greenland and Antarctica. You might wonder why those changes are important to us here in the Southeast. Let me use a couple of recent articles I have seen to add a bit of explanation.
Live Science has a dramatic time-lapse image sequence of a moving glacier in Antarctica showing how it is calving icebergs into the Southern Ocean. Scientists know that this process is speeding up and increasing the amount of ice that is added to the ocean over time, mostly due to rising temperatures although other things may also be contributing. The problem for us here in the Southeast is that this ice was on land, so as it enters the ocean, it adds to the volume of water in the sea and thus sea levels are rising. This is a direct threat to coastal areas of the Southeast, which are seeing more frequent flooding events and infrastructure along the coasts that are being inundated by the higher water levels. And as the speed of the glacier increases, the amount of ice being added to the ocean is accelerating, leading to sea level rises that are increasing over time. This is a one-way event, at least on human time scales, so once it is off of Antarctica (and Greenland), it is in the ocean for a long time and will keep sea levels higher than they have been historically.
Another article from The Guardian talks about how the ice sheet in Greenland is destabilizing under the warming climate, and how this may represent a tipping point towards a permanent change in global ice, similar to what I described above. In this case, as the ice melts, it gets shallower, and the top of the ice is exposed to air at a lower elevation, which is warmer than the air that used to be on top of the ice sheet (if you’ve ever climbed a mountain, you know it is colder at the top than the bottom). Since the air is warmer, the ice melts faster, accelerating the process.
Sea ice causes other changes to the global climate system. Sea ice acts as a natural barrier to evaporation and energy transfer in the Arctic by blocking the movement of water vapor and heat from the ocean to the air. If there is no sea ice present, then there is a lot more exchange of energy between the ocean and the atmosphere, and that can lead to large-scale changes in atmospheric circulation which drive the local weather. It also can increase the amount of water vapor available at high latitudes to create snow or rain, changing the hydrology there. One consequence of that is described in this article in Science Daily, which shows that the late frosts that have destroyed a lot of the wine crop in France this year may have been caused by the loss of sea ice in the Barents Sea.
Changes in sea ice, glaciers, and large ice sheets all contribute to changes we are seeing in the global climate in a number of ways, and so climatologists watch those changes carefully to see how our climate may change as a result. They are just one piece of the puzzle that is the global climate system, but an important once because of how ice affects the movement of energy and water from land to sea to air.