But it also means the ocean is beginning to heat up in a serious way. This may not sound like much, but it is. Shallow waters are warming up, fast. By the end of the century, if warming continues apace, shallow waters may be a full degree Celsius 1. Even incremental increases in temperature cause coral to bleach, for instance, a phenomenon plaguing the keystone species around the world. Combined with acidification, which we'll get to shortly, coral risks flat-out extinction by century's end. That's the conclusion of a study published in Science ; "Nearly every coral reef could be dying by if current carbon dioxide emission trends continue.
Meanwhile, because warmer water is quicker to evaporate, it means the ocean can fuel more powerful storms. Combined with higher sea levels, by , the ocean will be more prone to overwhelm nearby communities in the event of a hurricane or tropical storm. And while the warming waters will prove problematic everywhere, the heating will be most pronounced away from the equator.
Like the Arctic and Antarctic, where warmer water is melting icebergs and ice sheets from below, contributing to further sea level rise and robbing polar bears still the most famous mascot of global warming , walruses, and other animals of their habitats. Last year, the lack of sea ice forced 35, walruses to crowd together for the first time in observed history, making for one of the most iconic examples of polar warming in recent memory.
The Arctic region is warming twice as fast as the global average; thus, according to projections of climate agencies like NOAA and the UK's Met office, Arctic sea ice may be all but gone in the summers by century's end. Warmer waters ripen conditions for invasive species, too, which is why crabs from the Caribbean are showing up in northern waters. Marine life all over is being driven northward—fish are heading towards the poles. Sharks are spawning further north. Algae is more likely to bloom—warmer-than-usual temperatures in the Pacific have fueled the record-breaking toxic bloom currently stretching past California right now, for instance.
Predictions of Future Global Climate
Algal bloom. Image: NOAA. Finally, probably the most dire-sounding development of all: An expansion of marine dead zones, wherein oxygen levels become so low that little life can survive. Maybe the best known example is the massive dead zone in the Gulf of Mexico ; it's about the size of Connecticut. A number of studies have linked warming waters to the expansion of these dead zones, also known as hypoxia—fixtures that will become more or less permanent in our future ocean. They will be a permanent fixture" of our oceans, Gary Shaffer of the University of Copenhagen, who studies dead zones, told National Geographic.
His model "predicts that global warming could cause dead zones to grow by a factor of ten or more by the year ," according to NatGeo. Sediment churned up in the Gulf, which feeds the dead zone. Image: NASA. That's just the most dire prediction; we may not see dead zones of that size, but we'll probably see a lot more of them than we do now. The bottom line is that as the ocean warms, it will transform in a host of very unpredictable, sometimes radical ways.
So how hot does Gavin Schmidt think the oceans will be in ?
Empirical Study ARTICLE
Sea snails with dissolving shells. But we're not just boiling; we're risking an acid bath, too. About percent of all carbon emissions are drawn down directly into the ocean, where it forms carbonic acid. As a result, the pH in the surface ocean today is 0. And the most recent research shows that ocean waters are on track to become much more acidic by —up to percent more so. In other words, by the end of the century, the ocean will be twice as acidic as it was in preindustrial times.
Effects | Facts – Climate Change: Vital Signs of the Planet
That's what Taro Takahashi, a professor at Columbia University's Earth Institute who studies ocean acidification, tells me. He said that he agrees with the landmark study by Richard Freely that attempted to project acidification levels into the future. If we continue emitting carbon dioxide at the current pace, we're on target to hit parts per million by the end of the century we're at ppm now. In that case, Freely explains, "surface water pH will drop from a pre-industrial value of about 8.
So what's the big deal?
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Higher sea levels mean that deadly and destructive storm surges push farther inland than they once did, which also means more frequent nuisance flooding. Disruptive and expensive, nuisance flooding is estimated to be from percent to percent more frequent within U. The two major causes of global sea level rise are thermal expansion caused by warming of the ocean since water expands as it warms and increased melting of land-based ice, such as glaciers and ice sheets.
The oceans are absorbing more than 90 percent of the increased atmospheric heat associated with emissions from human activity. Sea level rise at specific locations may be more or less than the global average due to local factors such as land subsidence from natural processes and withdrawal of groundwater and fossil fuels, changes in regional ocean currents, and whether the land is still rebounding from the compressive weight of Ice Age glaciers.
In urban settings, rising seas threaten infrastructure necessary for local jobs and regional industries. Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, landfills—virtually all human infrastructure—is at risk from sea level rise. To squeeze or stretch the graph in either direction, hold your Shift key down, then click and drag. This graph source data shows differences from the long-term average global ocean heat content in the top meters of the ocean.
The main source of ocean heat is sunlight. Additionally, clouds, water vapor, and greenhouse gases emit heat that they have absorbed, and some of that heat energy enters the ocean. Waves, tides, and currents constantly mix the ocean, moving heat from warmer to cooler latitudes and to deeper levels. The heat energy eventually re-enters the rest of the Earth system by melting ice shelves, evaporating water, or directly reheating the atmosphere. Thus, heat energy in the ocean can warm the planet for decades after it was absorbed.
If the ocean absorbs more heat than it releases, its heat content increases. Knowing how much heat energy the ocean absorbs and releases is essential for understanding and modeling global climate.
As water warms, it expands, so estimates for ocean temperature can be deduced from sea surface heights. To get a more complete picture of ocean heat content at different depths, scientists and engineers also use a range of in situ temperature-sensing instruments. Known as Argo floats, the sensors drift through the ocean at different depths.
Every 10 days or so, according to their programmed instructions, they rise through the water, recording temperature and salinity as they ascend. When a float reaches the surface, it sends its location and other information to scientists via satellite, and then descends again. Seals have even been fitted with instruments to obtain temperatures in areas that are difficult to reach. Weise, California Sea Grant.
Scientists constantly compare data from satellites, floats, and probes to verify that the values they produce make sense. They process the range of measurements to calculate an estimate for global average ocean heat content every three months. Worldwide, most ocean basins had higher-than-average heat content in , according to the State of the Climate in , consistent with the long-term trend of ocean heat uptake due to global warming.
Global map showing where heat content in the top meters 2, feet of the ocean was higher orange or lower blue than the — average. NOAA Climate. Another interesting pattern is the stark contrast between much higher-than-average heat content in much of the North Atlantic and much lower-than-average heat content in the waters south of Greenland.
According to the report, this heat build up in the North Atlantic has persisted since , and the lower-than-average heat content south of Greenland has been in place since at least The reason for this pattern has not been entirely established, but it may be associated with a reduction in the Atlantic meridional overturning circulation.
More than 90 percent of the warming that has happened on Earth over the past 50 years has occurred in the ocean. Recent studies estimate that warming of the upper oceans accounts for about 63 percent of the total increase in the amount of stored heat in the climate system from to , and warming from meters down to the ocean floor adds about another 30 percent. Averaged over Earth's surface, the — heat-gain rates are 0.
Less than a watt per square meter might seem like a small change, but multiplied by the surface area of the ocean more than million square kilometers , that translates into an enormous global energy imbalance. Ocean heat content over time from the sea surface to a depth of meters 2, feet in shades of orange, and from , meters 6, feet in shades of purple. Different colors represent different data sets. Details can be found in Figure 3. The upper ocean and deeper ocean trends are both strongly positive, with exhibiting record-high values for both. In the present, warming of ocean water is raising global sea level because water expands when it warms.
Combined with water from melting glaciers on land, the rising sea threatens natural ecosystems and human structures near coastlines around the world. Finally, warming ocean waters threaten marine ecosystems and human livelihoods. For example, warm waters jeopardize the health of corals, and in turn, the communities of marine life that depend upon them for shelter and food. Ultimately, people who depend upon marine fisheries for food and jobs may face negative impacts from the warming ocean.