I often need to review the basics or I lose sight of the big picture. The fact that we are a water planet is a good example of this. As land animals we tend to forget that life on Earth is determined by what happens with our oceans. We talk about CO2 emissions, and climate change, storms and droughts, but the ocean is also changing.
We know that not all solar energy is reflected back into space. We call this the greenhouse effect. About 50 percent of the the energy reaches and warms the Earth. Land tends not to hold heat very well and re-radiates it back to space. Most solar energy reaching the Earth’s surface is taken up by our oceans, and the ocean is warming. Unlike the land, water tends to hold heat much longer. As the temperature increases, the ocean will eventually increase the rate that it releases that stored heat.
About 30 percent of CO2 in the atmosphere is taken up by the ocean. A significant portion of that is taken up by marine plant tissue through photosynthesis. This helps to lower the rate of GHG warming. Unfortunately we are experiencing a decline in marine life and marine biodiversity.
Ocean currents determine where there are productive fisheries and virtual deserts with little marine life. Heat and density determine how nutrients move horizontally and vertically around the globe. Warm water can undercut and melt coastal glaciers like the massive Jakobshavn in Greenland. Warm water expands and contributes to sea level rise. But recently, glacial melt has taken over as the dominant force behind rising sea levels. This melt water is fresh and tends to float on top of denser salt water. Fresh water melt can change the pattern of ocean currents. It can also prevent phytoplankton from rising close enough to the surface to carry on photosynthesis.
Marine plant life is responsible for up to 80 percent of atmospheric oxygen. That factoid tends to be overlooked by the media.
What happens in our ocean is a key element to what happens on land.
The Ocean Saves Us From Becoming Venusians
The thermal properties of water have kept our climate from turning our atmosphere into a boiling caldron of toxic gases like Venus. That capacity is changing rapidly as more heat is taken up by the ocean. It is changing ocean circulation, melting the Arctic ice cap and undermining coastal glaciers.
Fifteen percent of the food we eat comes directly from the sea. On land we depend upon rain to supply water for crops. The rain that fills lakes, recharges groundwater and fills drainage basins comes from our oceans. Increasing ocean temperature just 1℃ (1.8℉) increases evaporation between five and seven percent. As water vapor increases, there should be more precipitation, but it is no longer following historic patterns in distribution, timing or intensity.
Increasing water vapor presents another factor related to climate change. Water vapor is the most powerful greenhouse gas that accelerates global warming. As the warming increases, so does evaporation in what is called a positive feedback loop. In this case, “positive” isn’t a good thing. It only means it contributes to a process already taking place. So “positive” can be good or bad depending on the trend already taking place.
The Ocean Is a Major Market Force
Over 90 percent of trade moves over the ocean. Increasing storms, changing currents and wind patterns directly impact trade and the global economy. Major ports have been shut down because of hurricanes, tidal surges and storms. Ocean currents can increase or decrease the cost of transporting goods by container ships.
Once we thought the ocean was so vast that it seemed inexhaustible. For centuries we used it as a cesspool and dumping ground. The natural resilience of the sea mitigated our irresponsible behavior when our numbers measured in millions, but not 7.5 billion.
The five great ocean gyres are now filled with plastics and the flotsam of civilization. Our improving standard of living has disproportionately increased the waste we pour into the atmosphere and the ocean. About half of the CO2 we emit by burning fossil fuels is absorbed by the ocean. The good news is that this has slowed global warming. The bad news is that it is also changing the pH of the ocean. The ocean habitat is changing faster than most organisms can adapt. As the ocean and marine life changes, it changes Earth’s resilience to humanity and the hubris of civilization.
The ocean may have once seemed vast and inexhaustible. We may not have noticed the changes, yet they are profound. Today, we ignore the ocean at our own peril.
A topic to study and discuss: Living within planetary boundaries.