As the Great American IV speeds along the South Atlantic, the ocean will look much the same to Rich as it did during his race in 2008. But if you look closely, there have been some pretty big changes in our global ocean and in the climate of our planet. Let’s start with the biggest factor in human-caused climate change: Carbon dioxide in our atmosphere has steadily increased. In the eight years since 2008, its levels have climbed from 385 parts per million (ppm) to 407 ppm. Is this 22 ppm change a lot or a little? Measurements from air bubbles trapped in ice long time ago in the Antarctica show that this increase is much greater than what happened in the 2000 years before our industrial age. It is a lot, and it is happening quickly!
What does this mean for the ocean? Just like our atmosphere, the ocean has warmed also, but not the same everywhere. In places like the Arctic Ocean, the increase has been a lot. But elsewhere, like in the Southern Ocean that Rich is skirting right now, the ocean may actually have cooled a little. Why? The answer is the wind. What makes the wind blow is the difference in air temperature and pressure between two points. Cold air is denser and results in higher atmospheric pressure, and this high-pressure air wants to flow toward warmer, lower pressure, areas. As the planet’s atmosphere warms, these differences in hot and cold are getting bigger. An example is the difference between the Antarctic cold air and the surrounding sub-tropical warm air, and the result is that the winds in the ocean around Antarctica are getting stronger. These stronger winds cool the ocean through evaporation, just like, if you are a little sweaty, you’ll feel the wind start chilling you!
That, though, is climate, and what Rich has to worry about is weather—the storms and calms that our changing climate spawns. From a climate perspective, you’d predict that the storms on average have become a little stronger, but that doesn’t mean that all storms are more intense. Either way, let’s wish Rich and all the other skippers luck to avoid the worst ones!