How Does Climate Change Affect The Ocean – As climate change intensifies, its effects will be felt across the planet. The global ocean plays a key role and has so far absorbed most of the carbon dioxide and heat generated by human activity. But it is also vulnerable. Some significant changes are underway and climate disruptions in our oceans seem to be getting worse.
About 90% of the excess heat trapped in the atmosphere by greenhouse gases is eventually absorbed by the world’s oceans. Because the oceans are so large, the change in sea water temperature may seem small: the sea surface has warmed more than 0.5 degrees Celsius in the last century. It’s still enough to cause significant disruption, and warming is accelerating.
How Does Climate Change Affect The Ocean
When things heat up, they expand, become denser, and take up more space. Oceans are no different. Indeed, from 1993-2010, global warming is thought to have increased by an average of 1.1 millimeters per year, accounting for a large proportion of the overall increase we’ve seen.
What Is A Marine Heatwave?
In the year The total observed increase from 1993-2010 was 3.2 mm per year, with contributions from other sources, such as water stored on Earth as ice. (Graphics: Manuel Bortoletti / China Chat Ocean)
Warm waters affect the atmosphere above it. Warmer sea surface temperatures are associated with stronger hurricanes and tropical cyclones, which increase the number of Category 4 or 5 hurricanes that hit islands and coasts. Warmer waters can dissolve less carbon dioxide, which means more remains in the atmosphere to accelerate global warming.
As with land, ocean warming is creating harmful heat waves. Occurs when abnormal weather or water currents affect the average water temperature for at least five consecutive days. But it may take months or years. In the year A 2013-2015 North Pacific ocean heat wave killed up to a million seabirds along the west coast of the United States.
When carbon dioxide dissolves in seawater, it reacts to form carbonic acid: a relatively weak acid, but strong enough to change the pH of seawater, which is alkaline in nature. Since the industrial revolution, dissolved carbon dioxide is estimated to have lowered the average pH of the upper ocean by 0.1 pH units, from 8.2 to 8.1 (7 is neutral).
What Is Ocean Acidification?
This change may not seem like much, but since pH is measured on a logarithmic scale, it represents a 30 percent increase in acidity. This has a major impact on seawater chemistry and the ecosystems that depend on it.
Increased acidity is bad news for molluscs and other marine life that use the mineral calcium carbonate to build their shells and exoskeletons. More acidic water contains less of this mineral, which is less available to calcifying organisms such as oysters, mussels, sea urchins, shallow corals, deep-sea corals, and calcareous plankton. Worse, the change in chemistry promotes the breakdown of existing carbonate structures.
Coral is particularly vulnerable. Experiments on a small section of Australia’s Great Barrier Reef showed that artificially decarbonizing seawater, i.e. returning the pH to pre-industrial levels, increased coral calcification by 7%. Then, when scientists increased carbon dioxide levels and lowered the ocean’s pH to levels expected later this century, calcification dropped by a third.
As climate change continues, many scientists believe it is inevitable that the massive Greenland and Antarctic ice sheets will collapse and melt completely, eventually releasing enough water into the oceans to raise global sea levels by several meters. It will take time—hundreds, maybe thousands of years—but melting is accelerating. The United Nations Climate Body predicts that average sea levels could rise by 61cm by the end of the century under low-emissions conditions.
How Does Climate Change Affect Animals?
In the year By 2050, sea level rise could push the peak tides in countries currently home to at least 300 million people, particularly in Asia.
Residents of the Sundarbans are working to repair the dam that was damaged after the sea water flooded their rice fields. This lower delta region is located between the borders of India and Bangladesh. It is home to about 4.5 million people and is particularly threatened by sea level rise. (Image © Peter Caton / Greenpeace)
Coastal ecosystems are also affected. Coasts and wetlands experience more severe and frequent flooding and erosion, and sensitive freshwater habitats, including mudflats and marshes important for breeding bird species, are flooded.
Sea ice, which forms when seawater freezes each polar winter, is melting and melting each summer. The melting of this ice will not add much to sea level, but it will cause great problems for the organisms that depend on it. Polar bears in particular need sea ice to hunt seals, which studies show many of the 25,000 bears left in the Arctic are struggling to survive. The animal colony in the southern Beaufort Sea off Alaska and northeastern Canada declined by 40 percent between 2001 and 2010.
Climate Change In The Mediterranean
Ocean currents are sensitive to the effects of climate change. Today, these currents act as a giant global conveyor belt: As winds sweep the atmosphere from the warm equator to the cold poles, they drag the surface water along with them. Cooled by the cold polar air, this water becomes denser and sinks into the deep ocean, where it is pushed back into the equator (while still warming, shrinking, and rising) by the denser water above. . The cycles go round and round, transporting and mixing nutrients as they move.
Melting ice disrupts this system. A large volume of fresh water flowing over the pole reduces the volume of the seawater, causing it to sink more slowly. Without the same downward driving force, the entire global cycle can weaken. In the year In 2018, scientists suggested that the current in the Atlantic Ocean has decreased by 15%. And some studies They predict it could be over 30% worse by 2100.
Based on what happened in the past, scientists say that the slowing down of ocean currents can cause significant changes in the Earth’s atmosphere and thus the weather. European winters can be even colder (an idea taken to extremes). Meanwhile, the waters of the South Atlantic Ocean may warm, and as sea surface temperatures affect winds and precipitation, they may disrupt rainfall cycles important to crops in Asia and South America.
Ocean creatures depend on oxygen dissolved in seawater just as much as we breathe in the atmosphere. However, climate change is slowly draining oxygen from the oceans: between 1960 and 2010, it is estimated that 1-2 percent was lost, and by 2100 it could rise to 4 percent.
Climate, Nature And Our 1.5°c Future
There are several reasons. Warmer waters hold less gas, and the disruption of ocean currents limits the amount of oxygen transported from the surface to the depths.
It’s a growing problem when fertilizers and other nutrients added to farmland run into rivers and into coastal waters. Encouraged by an unexpected supply of food, algae grow and multiply rapidly, creating large floating blooms, sometimes called green (or red) waves. These can, for example, cause problems by releasing chemicals that are toxic to fish. As the algae die and sink, the microorganisms that decompose the blooms absorb oxygen from the surrounding water.
The beach of Gdansk in northern Poland was closed to tourists in the summer of 2018 due to the growth of toxic algae (Image: Wojciech Strozyk / Alamy)
In extreme cases, dissolved oxygen levels can be so low that parts of the deep ocean become barren. In the year A 2008 global study found at least 405 such dead zones, up from 49 in the 1960s. The Baltic was probably the worst hit. Despite efforts by neighboring countries to limit agricultural emissions, the Baltic Sea still contains a large dead zone about 70,000 square kilometers the size of Ireland.
Chapter 3: Oceans And Coastal Ecosystems And Their Services
Already under pressure from overfishing and pollution, marine life – from large fish to cyanobacteria – is being affected by climate change. As oceans warm and currents change, some marine life may move more easily, for example into colder polar waters. These changes in distribution have profound effects on everything from people trying to catch tuna to the species they feed on, to zooplankton. Under the stress of resource displacement, species are already weakened and are prone to acidification and lack of oxygen.
Changes in complex and interconnected food web systems are difficult to predict. Fishing in some areas may increase as important new species enter the net. But overall the effect can be bad. A study conducted last year found that warm water in 2010 Since the 1930s, sustainable catches have declined by 4 percent. The most affected sea was the Sea of Japan.
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