Humanity’s carbon pollution has the potential to turn oceans into a global warming “time bomb.” Ocean temperatures have spiked: NOAA data collection indicates ocean temperatures are probably the highest they’ve been in more than 100,000 years.
The data doesn’t lie: Ocean temperatures have remained above seasonal records for the past 6 weeks, resulting in more marine heatwaves. Global ocean temperatures set a record high for April at 0.86°C (1.55°F) above the long-term average. This marked the second-highest monthly ocean temperature for any month on record, just 0.01°C (0.02°F) shy of the record-warm ocean temperatures set in January 2016. On April 13, NOAA’s Climate Prediction Center announced an El Niño Watch alert status, as ENSO-neutral conditions are expected to last through the Northern Hemisphere spring with a 62% chance of El Niño developing May–July 2023. As the most relevant indicator of global warming, the ocean heat content (OHC) change is tightly linked to the Earth’s Energy Imbalance (EEI).
What is the relationship between climate change and the oceans? Approximately 93% of the EEI is stored in the oceans, and the heat change in the ocean system drives and reflects global climate change. Scientists say that the oceans have been warming unabatedly over the past few decades, and this trend will probably continue to increase rather than decrease in the future due to continuous global warming. Therefore, it is essential to effectively construct and predict the ocean heat content change and future ocean warming for coping with the climate crisis.
Why are heatwaves a consequence of warming oceans? Warmer ocean waters encourage frequent, lengthy marine heatwaves, where temperatures can jump several degrees or more above average. Warmer-than-average ocean temperatures are likely to persist or even intensify, bringing with them more extreme weather and marine heatwaves. For example, over the last decades, marine heat waves (MHWs) in the Mediterranean Sea have caused mass-mortality events in various marine species and critical losses for seafood industries. MHWs are expected to become more intense, longer, and more frequent.
What — or who — is to blame for rising ocean temperatures? Cycles have been profoundly altered due to the emission of GHGs and other anthropogenic substances, driving pervasive changes in the Earth’s climate system. To say it simply, oceans help with planet-warming gases by absorbing 90% of our human GHG-emitting human activities.
How can we tell that rising ocean temperatures are changing the planet? Changes in ocean heat content (OHC), salinity, and stratification provide critical indicators for changes in Earth’s energy and water cycles, according to experts. Property values, lives, and careers are all being altered due to more intense hurricanes, heavier rainfall, and deeper snowstorms.
Why should you care that sea temperatures are going up? Even the seemingly slight increase of 1.5°F in ocean temperature represents an enormous amount of heat, according to WHOI. The increase is large enough to transform marine biodiversity, change ocean chemistry, raise sea levels, and fuel extreme weather. If you think that it’s just coastal communities that experience the effects of rising ocean temperatures, think again. The effect resonates across land masses and bodies of water, at mountainside villages and urban centers. Warmer sea surface temperatures change annual weather patterns and expected precipitation, so that Italy gets once-in-a-century flooding, severe drought threatens the agricultural lands of central Florida, and devastating wildfires in Alberta, Canada burn more than 150 times the area than had occurred in the last 5 years.
What happens when sea surface temperatures increase? Higher sea surface temperatures disrupt the mixing of nutrients and oxygen that are key to supporting life and potentially alter the ocean’s crucial role in absorbing carbon from the atmosphere. Rising ocean temperatures contribute to oxygen-depleted ocean dead zones in large coastal and open ocean areas. Warmer water means increased evaporation, the risk of more intense cyclones, and consequences on ocean currents. The effects of heatwaves alone harm marine life, shift seasonal weather systems, and alter essential planet-regulation.” As we heat it up, the ocean becomes a bit like a time bomb,” oceanologist Jean-Baptiste Sallee, of the French research agency CNRS, told Phys.org.
What is the effect on marine life? Simultaneous ocean warming and acidification will alter marine ecosystem structure and directly affect marine organisms; marine life will suffer the most severe effects of heightened ocean temperatures. Fish species move northward to continue to locate cool temperatures and food sources, so fishers and their communities can lose their livelihoods. Hotter oceans can hold more carbon dioxide, which causes seawater to become more acidic. This phenomenon, known as ocean acidification, harms corals, clams, snails, and many other marine organisms, mainly by dissolving their calcium carbonate shells and skeletons. Warmer ocean temperatures mean that the ocean is physically less capable of holding dissolved oxygen, adding to the stress for marine life. Available habitats for many marine species shrink with ocean warming and deoxygenation. Prolonged periods of heat wreak havoc on marine health and increase the risk of massive bleaching events on Australia’s Great Barrier Reef and other sensitive coral ecosystems.
If we stop using fossil fuels, won’t the ocean stop warming? Ocean temperatures will continue to increase long after any surface temperature stabilization that results from eliminating fossil fuels from human use. As they do so, they trigger problems for marine life from corals to whales.
Are warming ocean temperatures contributing to sea level rise? Definitely. This thermal expansion may be the biggest causal factor of sea level rise over time. That’s because water becomes less dense and expands as it heats up, so it takes up more space and causes sea levels to creep up. Then polar ice sheets decrease and deconstruct, pushing water levels even higher. WHOI scientists estimate sea level could rise at least 15 inches by 2100 in some areas, potentially displacing millions worldwide.
Are heightened ocean temperatures new? The deep ocean historically has adapted to temperature changes over millennia rather than decades. “We are in a new climate state,” Jens Terhaar, ocean biogeochemical modeler at WHOI, reveals, “extremes are the new normal.”
While the recent SST anomaly is terrifying, it is not unexpected. CMIP6 models predicted the monthly 0.7°C anomaly (comp. to 1982-2011) to be reached between 2017&2040. This wouldn't have happened without climate change, we are in a new climate state, extremes are the new normal. https://t.co/qaAjJdxwGy pic.twitter.com/0a1B28E7dx
— Dr Jens Terhaar (@JensTerhaar) April 24, 2023
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