More than 90% of the extra heat generated by climate change is being taken up by the world’s oceans. On July 31, the global average sea surface temperature set a new record of 69.73 degrees Fahrenheit, as reported by the Earth observation program of the European Union's Space program. This heightened ocean temperature has consequences such as more intense storms, displacement and death of fish, disruption of coral reefs, stimulation of growth in harmful algal blooms, and long-term sea level rise.
The oceans cover 70% of the earth's surface and, due to their highly efficient heat capacity, absorb the majority of warming caused by global warming. Baylor Fox-Kemper, professor of earth, environmental and planetary sciences at Brown University, points out that "over 90 percent of the excess energy on earth due to climate change is found in warmer oceans, some of it in surface oceans and some at depth." Carlos E. Del Castillo, head of NASA's Ocean Ecology Laboratory, uses the example of two pots being placed on a stove, one with water and one without, to illustrate the efficiency with which water absorbs energy. He emphasizes, however, that the science is slightly more complex than this.The effects of climate change are becoming increasingly evident in record ocean temperatures, such as the 101-degree water off the coast of Florida. Benjamin Kirtman, professor of atmospheric sciences at the University of Miami, explains that this is "consistent with a continued increase in extreme weather in the climate system, that is more heat waves and marine heat waves, droughts in already dry regions, floods in already wet areas, extreme winds, and fire.” He adds that the more greenhouse gasses emitted, the more heat the seas will absorb. In short, Kirtman states, "Greenhouse gas warm the entire climate system including the ocean. Put simply, the greenhouse gases serve to trap more heat, some of which is absorbed by the ocean."
On July 31, the global average sea surface temperature, which is monitored by Copernicus (the Earth observation component of the European Union's Space program) reached an all-time record of 69.73 degrees Fahrenheit. This temperature was measured at approximately 33 feet beneath the ocean's surface, and the term "global" is used to define the extrapolar regions that are between 60 degrees north and south latitudes. This particular record has been kept since 1979, but July was the hottest July on record with an anomaly of 0.92 degrees Fahrenheit. Gavin Schmidt, the director of the NASA Goddard Institute for Space Studies, said that March is typically the warmest time of the year since the southern hemisphere has more ocean and this particular record set in March 2016. The sea surface temperature in all ice-free oceans also reached a record-high in July, reported Copernicus. "It's not just that it's hot, it's the rate of the warming. We haven't seen rates of warming this extreme in the past," Kapnick said.
Multiple factors, including El Niño, are responsible for the present surge in sea surface temperatures. Fox-Kemper explained to CNBC, "Climate variations such as El Niño in the Pacific and an analogous pattern in the Atlantic have intensified in combination with the permanent ocean warming due to global warming." He went on to add, "It would be almost inconceivable to reach these temperatures without the additional heat generated by human-induced greenhouse gas emissions." Zeke Hausfather, a data scientist at Berkeley Earth focusing on climate science and policy, stated to CNBC that humans are, in fact, responsible for introducing the equivalent of a continuous El Niño effect every five to ten years. Castillo informed CNBC that the last ten years have been "the warmest since at least the 1880s in terms of sea surface temperature." Sarah Kapnick, NOAA's chief scientist, revealed to CNBC through a spokesperson that 44 percent of the global ocean is presently going through a marine heatwave, which is the highest percentage since 1991. A marine heatwave is a situation where sea surface temperatures are higher than 90 percent of previous observations for the region and time of year, as per NOAA. Kapnick brought attention to the fact that the rapid warming of the ocean is even more alarming than its temperatures. "It's not just that it's hot, it's the rate of the warming. We haven't seen rates of warming this extreme in the past," she stated.
Fox-Kemper stated that the most powerful storms on earth - hurricanes and tropical and extratropical cyclones - receive a great deal of their energy from the humid air which is close to the ocean surface. The warmer the seawater, the higher the temperature and humidity of the air and, in turn, the more power it can yield, leading to more intense storms. This explains why powerful storms are most likely to occur along the warm ocean currents like the Gulf Stream and Kuroshio in the Northern Hemisphere, Fox-Kempler added.
Water vapor evaporating from the ocean surface, a major driving force in stronger storms, is a variable of ocean temperatures and wind speed and its connection to temperature is "highly non-linear," Kirtman explained to CNBC, indicating that even small changes in temperature can lead to substantial increases in evaporation. Water vapor condensing releases heat into the atmosphere, creating a self-reinforcing cycle. "More atmospheric moisture means more condensational heating, which enhances the storm," he declared.Michael Lowry, hurricane specialist and storm surge expert, told CNBC that the effect of ocean temperatures on hurricane formation differs from one region to another. Temperature rises in the key development region of hurricanes, such as in the south of the 20 degrees latitude in the deep tropical Atlantic, are especially impactful. "This is what NOAA was taking into consideration when they issued their hurricane forecast last week," Lowry stated, referring to the weather agency's prediction that warmer oceans will result in a more strenuous hurricane season.No matter where a hurricane takes shape, the hot seas will amplify it. Lowry remarked, "It's like having dry powder--it only takes one."
Fish species have defined temperature preferences in order to survive. Rainer Froese, senior scientist at the Helmholtz Centre for Ocean Research in Germany stated that when temperatures reach the upper tolerance range, growth and reproduction become hindered. At the upper lethal temperature range, fish will die. To avoid these temperatures, migratory fish may move from Florida to New York or from New York to Nova Scotia, as Daniel Pauly, professor at the University of British Columbia's Institute for the Oceans and Fisheries, noted to CNBC. He further explained that individuals have been observed moving into areas they weren't previously found in during the summer months.
According to Lorenz Hauser, Professor at the School of Aquatic and Fishery Sciences in Seattle, increased water temperatures can be dangerous for fish for two reasons. Firstly, warmer water contains less oxygen than cold water but requires more oxygen to meet the metabolic demands of fish. Secondly, as the temperature rises, fish need more food to remain healthy and grow, yet there may not be enough prey available for them to consume. Daniel Pauly, another expert in the field, added that bigger fish have more difficulty adjusting because their gill surface area does not increase at the same rate as their overall weight. This means that they cannot get enough oxygen fast enough when a sudden increase in ocean temperatures, such as a heat wave, occurs. Thus, a mass die off is likely to be seen in cases where fish cannot adjust fast enough. Michael Froese, another expert, warned that these changes in temperature are likely to lead to significant changes in species composition, with some species dying out due to competition with new species or predation.
Coral reef populations are being drastically diminished by the rise in ocean temperatures. The Coral Restoration Foundation, a non-profit organization in Florida that focuses on coral reef restoration, has been relocating coral from the sea into land-based holding tanks. Phanor Montoya-Maya, Restoration Program Manager at the Foundation, declared in a statement on July 20th that the team which visited Sombrero Reef - a site Coral Restoration Foundation have been working on for over a decade - witnessed a heartbreaking 100% coral mortality rate. Furthermore, almost all the corals in the Looe Key Nursery in the Lower Keys have been lost.
Castillo informed CNBC that coral reefs usually do best in temperatures between 73 and 84 degrees Fahrenheit, yet still can exist at higher and lower degrees for a short while. He explained that the current hot ocean temperatures in Florida are causing severe coral bleaching events, where the coral is so overstressed that it expels the vital algae, zooxanthellae, which is needed for survival. Castillo added that the coral can often regrow its zooxanthellae following bleaching but can be significantly weakened by the experience; in the current heat wave, even outright coral die offs have been documented. Castillo also noted that coral reefs are essential to marine life, as one-fourth of species rely on them in some way.
"Microorganisms thrive in warm temperatures," said Hans W. Paerl, professor of marine and environmental sciences at the University of North Carolina at Chapel Hill's Institute of Marine Sciences to CNBC. "These conditions create a favorable environment for their rapid growth, resulting in the development of harmful algae blooms containing dinoflagellates, diatoms (also known as microalgae or red tide), and cyanobacteria (also known as blue-green algae)."
People and animals can get sick if they are exposed to algal blooms or ingest seafood that has come into contact with them. The Centers for Disease Control and Prevention have reported that the severity of the illness is contingent upon the type of algae and the duration of exposure. The intensification of these algal blooms is caused by nitrogen and phosphorus from fertilizer runoff entering bodies of water, a material that is increased with climate change due to an intensified cycle of storms and dry season. Prof. Hans Paerl of UNC-Chapel Hill notes that big storms will carry more of this fertilizer runoff into coastal areas, leading to increased growth of algae and bacteria, consequently creating oxygen-depleted dead zones with severe impacts on ecology and fish populations. Furthermore, as the oceans warm, these blooms are migrating to previously uninhabited cooler waters, says Christopher Gobler of Stony Brook University. This phenomenon is particularly concerning as the pathogens could be unfamiliar to those regions, often resulting in mass deaths and illnesses.
Gary Griggs, professor of earth and planetary sciences at the University of California in Santa Cruz, told CNBC that when water is heated, it expands.
Broadly, warmer oceans will lead to an increase in sea level and associated coastal flooding risk. This is caused by thermal expansion of the oceans. Kirtman notes that this is a positive feedback, which amplifies the warming, as less sea ice is present in higher latitudes. Griggs mentions that two-thirds of the global sea level rise is due to ice melt from Antarctica, Greenland, and other continental glaciers, and the other third is from a temperature increase. It should be noted, however, that individual record-high temperatures do not generally lead to any observable changes in sea level, as there is approximately 330 million cubic miles of sea water, and it takes a substantial amount of heat to increase sea level rise.
Judith Kildow, founder and director emeritus of the National Ocean Economics Program, informed CNBC that it is too early to measure the economic impact these record sea surface temperatures have had. She added that people relying on the oceans are adapting. For instance, some fishermen have begun to convert their boats into whale watching enterprises since they can no longer fish with success. Kildow also pointed out that this situation has far-reaching effects, such as bleached coral reefs, higher sea levels due to warming, the migration of fisheries north, and the decrease in the value of coastal real estate. Even stronger storms caused by warmer waters will ravage coastlines, and the value of property nearby will plummet.
Asked if there were any benefits to the warming oceans,NASA's Schmidt jokingly commented “Slightly extended beach swimming period?” To rectify this whole array of consequences, it is essential to lessen the burning of fossil fuels, including methane and nitrogen oxides. Kildow emphasizes that “that's one thing we should all be doing is consuming and burning less fossil fuels.”
Comments