Part 2 – The impact of climate change on Puerto Rico: Beyond weather

Cade Johnson notes that the temperature average in Puerto Rico, like in the surrounding seas, has increased slightly in recent decades.
In the first article of this series, we noted the publication of a PR Climate Plan and briefly explored why human activities have led to the need for such a plan. In this brief article, let’s examine how climate changes are not just weather changes.
The average temperature in Puerto Rico, like that of the surrounding seas, has increased a little in recent decades. We can sense this from temperature records. But rising temperatures have an additional consequence: When water gets warm, it expands.
As a result, sea levels have been steadily rising. Warmer air has also melted large amounts of ice perched on land-based glaciers, and this old frozen water has returned to the sea. Together, these phenomena have raised sea levels about 3/4 inch per decade through the late 20th century, with an even faster rise in recent decades.
The Intergovernmental Panel on Climate Change (IPCC) predicts further sea level rise under various scenarios, but there is much uncertainty about the exact rate because of two factors. First, we do not fully understand how melting ice in Greenland may affect the ocean current system of the Atlantic Ocean, called the Atlantic Meridional Overturning Circulation, or AMOC (of which the Gulf Stream is the best known part); and, second, we do not know how rapidly glaciers in Antarctica may move as coastal ice shelves break up in the warming sea.
Changes to either of these factors could affect the rate of sea level rise. Based on what we know right now, the rate of sea level rise is projected to increase by about 3 inches per decade — a pace about four times greater than the rate we’ve seen previously.
When people who study glaciers talk about sudden changes or rapid motion, we who are unfamiliar with glaciers might picture sudden and rapid activity like a startled horse. But glaciers really are “glacial” in their movement — if they move 10 times faster, you still can’t see them move. Nevertheless, like a gradually warming ocean, an accelerated glacier cannot be stopped.
And the faster-moving glacier is carrying water that was piled on land into the sea at a faster rate — like adding ice to a partly full glass of water. A “sudden” widespread glacial collapse in Antarctica will not create a tidal wave, though it could contribute an additional and devastating sea level rise of perhaps as much as an extra inch per year.
Part of the extra carbon dioxide we produce is dissolving in the ocean and making it less alkaline. Right now, seawater near the surface does not tend to dissolve carbonate minerals like limestone, seashells or coral reefs, but at greater depths there is a point where carbonate does dissolve. This point is known as carbonate compensation depth (CCD) and occurs at around 4300 meters (2.7 miles) below the surface.
As more carbon dioxide dissolves, the CCD gradually rises in the ocean. This process occurs slowly because it takes a long time for carbon dioxide dissolving at the surface to reach the deep ocean.
As the CCD rises to the depth of deep coral reefs, they will dissolve. As the CCD rises to the depth of deep clam species, they will perish. As the CCD reaches shallower depths, the ecosystems built on hard-shell organisms will collapse. We do not know how shallow-water ecosystems interact with those deeper ecosystems, so we cannot predict what the effects will be.
In these first two articles of this series, we’ve seen how carbon dioxide accumulation from burning of fossil fuels is heating the Earth, changing the climate and altering the world’s ocean systems.
In future articles, we’ll look at how Puerto Rico can address the changes we know are on the horizon and how our community can actually derive some long-term benefit from these dire circumstances.

Author Cade Johnson is a retired chemical engineer (Georgia Tech ’83) and a volunteer with the 501(c)(3) Exaquest Carbon, based in California. He has been volunteering with various climate response organizations for almost 10 years and has lived in the Caribbean since 2001 — currently in Naranjito, Puerto Rico. Send comments to [email protected].