Climate Change and the Oceans
Here is some news from our friends at National Environmental Education Foundation (NEEF) about the oceans of the world.
The news is super interesting (and a little bit scary), but hopefully it will inspire you to learn more about the ocean and become an ocean advocate. The text below is used with permission from NEEF.
Our oceans, despite having human-made ‘boundaries’ and names that makes them seem separate, and being thousands of miles apart the worlds oceans are really just ONE huge body of water. These oceans, from the frigid reaches of the Southern Ocean around Antarctica, to the balmy stretches of the Caribbean Sea, to the icy waters surrounding the Aleutian Islands, are connected through a deep-ocean current called the global ocean conveyor belt. This global circulation pattern helps to cycle nutrients and energy across the planet, supporting the world’s food chain and creating a dynamic marine environment.
Global Ocean Currents and Climate Change
This global current is powered by changes in ocean chemistry in different parts of the world. Local differences in seawater temperature and levels of salinity give different parcels of water varying densities, causing them to sink or rise in the water column.
Very cold, salty water, such as you would find in the Arctic Ocean where the formation of sea ice excludes salt and increases the salinity of the surrounding waters, is very dense, and thus sinks thousands of meters down to the ocean floor. Once at the bottom of the water column, this cold, dense water spreads out to make room for incoming water that is continuing to chill and sink from the surface. This sinking motion pulls in more water from the surrounding surface, creating a current.
As it spreads at depth, the dense, cold water has nowhere to go but south. It moves across the floor of the Atlantic Ocean, past the equator, and on towards the Antarctic continent, where it’s pushed around the southern landmass and fed more cold, salty water sinking from the surface. From here, the waters split—some of it is pushed back north towards the Indian subcontinent, and the rest of it moves up towards the North Pacific.
On this journey north, the waters are warmed by the sun, becoming less dense and rising up in the water column. Once the water reaches its new, higher position in the water column as a result of surface winds, equatorial heat influx, and salinity reduction, it once again spreads to make room for more rising water parcels, creating the second half of the current of the global ocean conveyor belt.
This global current is vital in providing for the planet’s ecosystems, but it is at risk of being impacted by climate change. Learn more about how climate change is affecting the ocean and ocean currents. If you’re heading out to the beach this summer, just ask yourself—where else in the world has this water been?
Global Ocean Temperatures on the Rise
- The average global sea surface temperature has increased about 1.5oF since 1901, an average rate of 0.13oF per decade.
- The average global sea surface temperature has been consistently higher during the past three decades than at any other time since reliable records began in 1880.
Oceans cover more than two-thirds of the earth’s surface and play a very important role in regulating the earth’s weather and climate. Currently, oceans absorb more than 90% of the heat that is trapped in the atmosphere from increasing levels of greenhouse gases, which raises the temperature of the water at the sea surface.
Since the oceans continually interact with the atmosphere through the water cycle, an increase in the average global sea surface temperature can have profound impacts on climate and weather systems. A higher sea surface temperature has led to an increase in the amount of water vapor over the oceans, increasing the risk of heavy rain and snow events. This higher temperature also has the potential to shift storm tracks and contribute to droughts in some areas.
A warming ocean temperature also contributes to sea levels to rise through thermal expansion, the distribution of many marine species to shift due to their dependence on specific water temperatures and nutrient availability, and changes the circulation patterns of deep ocean currents that transport warm and cold water around the globe.
The graph below shows how the average global sea surface temperature has changed from 1880 to 2015.