How is Climate Change Impacting Our Oceans?
All of us have heard of climate change and when we think of its effects, we picture images of summer heatwaves and winter flooding. We often forget the ocean is being affected too as it silently absorbs our carbon dioxide emissions while the disastrous effects lie deep under the waves, rendering them almost invisible to us. Yet oceans are essential to our lives for many reasons, no matter how far we live from the coast. They store our excess carbon, produce oxygen and sustain food stocks and our economy, meaning all these impacts need to be halted as soon as possible. So here is a short summary of what is really happening under the surface both in the future but also right now as you read.
Roughly 25% of all carbon dioxide emissions are absorbed by the ocean and stored deep down under the surface, keeping these warming gases safely out of our atmosphere. The seas also naturally absorb a lot of our planet’s heat but since 1950 when consumerism and production really kicked in, 90% of the earth’s warming in those 70 years has gone straight into our oceans. Had all this heat been left to circulate around our atmosphere, the temperature would have jumped by 56°C! Usually this heat is stored in the upper layers of the sea, yet this enormous level of heat is travelling down with the top one kilometre of water now warmed above average. This may impact global circulation currents, something we have always seen as a force of nature, something we cannot alter due to their sheer natural force. Well, now we have managed to control this too. Already the Gulf Stream is on an unprecedented slowdown which means less warm water and wind will travel from Mexico across the Atlantic to Europe. The Gulf Stream actually shut down completely 11,000 years ago due to substantial changes in global climate and this plunged Europe into an ice age!
This shutdown of global systems is not caused by the increased water temperature itself. Many of us think climate change means more heatwaves and milder winters and this because the term ‘global warming’ is in some ways misleading. Not all areas will warm under climate change. Some parts of Europe are predicted to actually get a little colder and when it does rain, the amount of water that falls will be intensified. It is this increase in freshwater entering our oceans which will alter the density of the water and impact global circulation systems, shifting bands of tropical rainfall which will alter both the African and Indian monsoon seasons.
On the subject of weather, hotter oceans equal more tropical storms. Large storms known as hurricanes, typhoons and cyclones form around the Equator in areas where the surface of the sea is over 26°C. If 2-3°C of warming occurs globally, each of the storms formed will be able to hold 25% more water which is released when the storm hits land, causing extraordinary damage to the coastlines at its mercy.
Heat further impacts the biodiversity in the sea with coral bleaching occurring when temperatures are 1°C above the monthly maximum. Bleaching occurs when corals become stressed and kick the algae living side by side with them out of their space. These algae are what give corals their colour and so without them, our reefs appear bleached white and are also a lot more susceptible to disease as they are no longer receiving nutrients from the algae. Dying coral reefs are devasting for our oceans as they form the base of the food chain, supporting the growth of small fish and provide a feeding ground for many ocean creatures.
Ocean acidification is a further new threat to corals. As the oceans absorb nearly one third of carbon dioxide emissions, this carbon turns into carbonic acid once it hits seawater which, since the industrial revolution, has caused our oceans to become 30% more acidic. This impacts corals as well as other organisms who have shells which are made of calcium carbonate, a substance which dissolves in these newly acidic conditions. This makes it increasingly hard for corals and other creatures like molluscs to build their skeletons, impacting survival. It’s not just corals at threat either as the first creature to go extinct because of modern climate change has already been lost. The Bramble Cay Melmoy, a small rodent, only lived on coral islands in the Great Barrier Reef, evolving over one million years, however increasing storm surges and rising sea levels meant their home was suddenly swept away before scientists could start a captive breeding programme to increase their numbers. If we don’t take action to halt our emissions, many more species will soon be lost to this almost invisible threat. Turtles are in grave danger under climate change as the temperature of the sand surrounding their eggs determines whether they hatch as male or female. As global temperatures increase, we are seeing more females being born with Raine Island in Australia showing an extreme case study. Here, the sands got so hot that female hatchlings now outnumber males 116 to 1, clearly placing future populations in jeopardy.
All these effects of climate change will inevitably come back round to us and impact our own lives. Melting sea ice is increasing sea levels by averagely 3.2 millimetres per year. However, this is a global figure when in fact changes in sea level depend on a range of local factors such as erosion, the amount of impermeable concrete surfaces and groundwater extraction which causes the land to subside. The northern part of the city of Jakarta is sinking by up to 25 centimetres per year as more and more water is extracted from under the ground, causing the earth to subside and the sea to flow easily into the streets.
Our fish stocks are also threatened as ocean species like cod are moving poleward by averagely 78 kilometres every decade to get to colder waters which means countries are losing their income as well as food. Three billion people worldwide rely on fish for their primary source of protein but these nutritional staples could soon be swimming away from their coastlines. Several nations are already preparing themselves as some of the first climate refugees, with the Maldives constructing artificial islands at a higher level above sea level while other island nations secure places for their inhabitants in new countries such as Australia and India.
The list of climate impacts is endless. It seems clear we will soon be reaching the ocean’s limits if we carry on consuming at top speed. Yet oceans can also be our solution to the climate crisis. Geoengineering techniques are already looking at how the oceans can be altered to absorb more carbon dioxide while they hold immense possibilities for clean, renewable energy. We are now at a crossroads; do we carry on abusing our blue planet or do we overhaul our system to secure a better future? Which pathway will your individual actions support?
By Neve McCracken-Heywood