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Unlock This CourseOur oceans cover over 70% of Earth's surface and play a crucial role in regulating our planet's climate. However, human activities are causing rapid changes to our climate system and the oceans are bearing the brunt of these changes. Understanding how climate change affects our marine environments is essential for protecting ocean life and the billions of people who depend on healthy seas.
Key Definitions:
The oceans have absorbed over 90% of the excess heat from global warming. This causes water to expand, contributing to sea level rise and disrupts marine ecosystems. Warmer waters hold less oxygen, creating dead zones where marine life cannot survive.
Climate change is transforming our oceans in several interconnected ways. These changes don't happen in isolation - they work together to create complex challenges for marine life and coastal communities worldwide.
Global sea levels have risen about 23 centimetres since 1880, with the rate of rise accelerating in recent decades. This happens for two main reasons: thermal expansion of seawater as it warms and the addition of water from melting glaciers and ice sheets.
As ocean water warms, it expands and takes up more space. This accounts for about half of current sea level rise.
Greenland and Antarctic ice sheets are losing mass rapidly, adding billions of tonnes of water to the oceans each year.
Mountain glaciers worldwide are shrinking, contributing fresh water to the oceans and affecting local water supplies.
The Maldives, a nation of 1,200 coral islands in the Indian Ocean, faces an existential threat from sea level rise. With an average elevation of just 1.5 metres above sea level, even small increases in ocean levels threaten to submerge entire islands. The government has implemented innovative solutions including floating cities and artificial island construction, whilst also becoming carbon neutral to lead by example in climate action.
Whilst much attention focuses on carbon dioxide in the atmosphere, the oceans have quietly absorbed about 30% of all human-produced CO₂. This might sound helpful, but it's creating a serious problem called ocean acidification.
When carbon dioxide dissolves in seawater, it forms carbonic acid, making the ocean more acidic. Since the Industrial Revolution, ocean pH has dropped by 0.1 units - this might seem small, but pH is measured on a logarithmic scale, so this represents a 30% increase in acidity.
More acidic water makes it harder for creatures like corals, oysters and sea snails to build their shells and skeletons. This affects the entire food chain, as these organisms form the base of many marine ecosystems.
Ocean currents act like a global conveyor belt, moving warm and cold water around the planet and helping to regulate climate. Climate change is disrupting these vital systems.
The Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream, is weakening due to increased freshwater from melting ice. This system brings warm water north and cold water south, helping to keep Europe warmer than it would otherwise be.
The Great Barrier Reef has experienced unprecedented back-to-back bleaching events in 2016, 2017 and 2020. When water temperatures rise just 1-2°C above normal for several weeks, corals expel their symbiotic algae, turning white or "bleaching". Without these algae, corals cannot get enough food and may die. Scientists estimate that half of the Great Barrier Reef's corals have died since 2016, making this one of the most visible examples of climate change impact on marine ecosystems.
Climate change affects marine life in numerous ways, from shifting species distributions to altering food webs. Many species are struggling to adapt to the rapid pace of change.
Many fish species are moving towards the poles as waters warm, disrupting traditional fishing grounds and local economies.
Arctic sea ice loss threatens polar bears, who depend on ice platforms for hunting seals.
Rising sand temperatures affect turtle nesting beaches, skewing sex ratios as warmer sand produces more female hatchlings.
Despite the challenges, there are many ways we can help protect our oceans from climate change impacts. Conservation efforts work at local, national and international levels.
Creating no-take zones and marine reserves helps ecosystems build resilience to climate change. Healthy, diverse ecosystems are better able to cope with environmental stress.
Protecting coastal habitats like mangroves, salt marshes and seagrass beds is crucial. These "blue carbon" ecosystems store massive amounts of carbon - up to 10 times more per hectare than tropical rainforests.
Everyone can contribute to ocean conservation and climate action. Small changes in daily life can add up to make a significant difference.
Use less energy, choose sustainable transport and support renewable energy to reduce CO₂ emissions.
Choose sustainably caught fish and support fisheries that use environmentally friendly practices.
Participate in local beach clean-ups and reduce plastic use to prevent ocean pollution.
In the Caribbean, scientists are using innovative techniques to restore damaged coral reefs. They grow coral fragments in nurseries, then transplant them to degraded reefs. Some projects have achieved survival rates of over 80%. Additionally, researchers are developing "super corals" that can better tolerate warmer, more acidic conditions. These efforts show that whilst climate change poses serious challenges, human ingenuity and dedication can help marine ecosystems adapt and recover.
The future health of our oceans depends on the actions we take today. Whilst the challenges are significant, there's still time to make a difference. By understanding the science, supporting conservation efforts and making sustainable choices, we can help ensure that future generations inherit healthy, thriving oceans.
Remember, the oceans don't just affect marine life - they regulate our climate, provide food for billions of people and support countless livelihoods. Protecting them is protecting our own future on this blue planet.