Climate Change and Our Changing Gulf

This article is part of a series written for the Sierra Club’s Blue Whale Campaign
to protect the Gulf of Saint Lawrence. Other articles examine our abundant marine life including whales, sea turtles and other threatened species. To view more articles, please visit the Blue Whale Campaign blog under the Blog tab…

By Colin Jeffrey

The world’s oceans are some of the most stable systems on the planet. Due to their massive size these bodies of water react slowly to atmospheric changes and play a pivotal role in creating our weather and climate. Vast amounts of ocean water evaporate into the air producing rainfall across the globe while ocean currents moderate our temperatures, transporting warm water towards the poles and cool water towards the equator. It takes a lot of effort to change earth’s stable oceans, but two hundred years of accelerating anthropogenic CO₂ production seems to be doing the trick. Since the industrial revolution began, our oceans have absorbed at least ninety percent of the heat and a third of the carbon dioxide (CO₂ ) produced by the fossil fueled greenhouse effect. These two inputs are changing marine ecosystems and processes. Moreover, the pace of change is accelerating rapidly as carbon dioxide emissions skyrocket.

In Atlantic Canada’s Gulf of Saint Lawrence, climate change is beginning to make its presence felt in several ways. Perhaps the most alarming development is increasing acidity in Gulf waters caused by the absorption of carbon dioxide. As CO₂ levels in the atmosphere have increased, the oceans have absorbed larger quantities which has already increased the acidity of ocean water by 30 percent. Further increases will be harmful to most marine life, particularly the many species that have shells and skeletons made of calcium carbonate since this compound is more water soluble in acidic conditions. While changes in the acidity of surface water in the Gulf of Saint Lawrence are not yet large enough to cause serious damage to marine life, acidification has increased by almost 100 percent in the deep waters of the Gulf. It appears that several factors have combined to acidify the Gulf’s deep water, particularly in the estuary of the Saint Lawrence river. Since the 1930s there has been a decrease in the amount of cold, oxygen rich water from the Labrador current entering the Gulf through deep channels. At the same time demand for oxygen has increased, most likely from an increase in microbial activity due to larger nutrient inputs from agriculture and other human activities. A 2°C temperature increase in deeper waters since the 1930s has led to further oxygen use as marine organisms become more active. Decomposing nutrients and the activity of marine organisms both produce carbon dioxide, which acidifies the surrounding water. Because these deep waters do not mix very much with other water layers, depleted oxygen is not replenished and the water gradually becomes more acidic. If the phenomenon of oxygen depletion and increasing acidity continues to spread in the deep waters of the Gulf, most bottom dwelling marine species will be negatively affected.

While impacts in the Gulf of Saint Lawrence from human driven climate change are currently small and localized, that is set to change as projected increases in CO₂ emissions drive the most rapid climatic change ever experienced on the planet. According to the Intergovernmental Panel on Climate Change, while similar increases in temperature did take place more than 20 million years ago, they happened over thousands of years instead of several hundred, offering some marine species time to adapt to changing conditions. If carbon emissions are not heavily reduced in coming decades, at least 30 percent of our marine species are at risk of extinction. With forecasts like this on the horizon, the current efforts of Newfoundland and Quebec to expand offshore oil and gas drilling into the Gulf make little sense. According to the latest scientific research on climate change the best thing we can do to protect our Gulf and all Canadian waters is get serious about reducing fossil fuel use.