Feedbacks: Climate Change Reducing Ocean’s Carbon Dioxide Uptake and accelerates Hypoxia States
Compilation of recent Ocean Science
- Climate Progress, Joe Romm reports Climate Change Reducing Ocean’s Carbon Dioxide Uptake
- Trenberth on Tracking Earth’s energy
- Solve Climate exclusive from Reuters Climate Change Drives Disease in Crucial Seaweed Species, Study Finds
- Ocean’s Harmful Low-Oxygen Zones Growing, Are Sensitive to Small Changes in Climate
- Waiting to Inhale: Deep-Ocean Low-Oxygen Zones Spreading to Shallower Coastal Waters
“The ocean is taking up less carbon because of the warming caused by the carbon in the atmosphere,” says [Galen] McKinley, an assistant professor of atmospheric and oceanic sciences and a member of the Center for Climatic Research….
McKinley is the lead author of a new analysis in the journal Nature Geoscience (subs. req’d) that appears to resolve a major issue in climate science: “How deep is the ocean’s capacity to buffer against climate change?”
We now know that as the ocean warms up, its ability to act as a carbon “sink” is diminishing. We are seeing a dangerous, amplifying carbon-cycle feedback.
The study’s news release explains:
As one of the planet’s largest single carbon absorbers, the ocean takes up roughly one-third of all human carbon emissions, reducing atmospheric carbon dioxide and its associated global changes.
But “whether the ocean can continue mopping up human-produced carbon at the same rate” wasn’t entirely clear. “Previous studies on the topic have yielded conflicting results.”
Back in 2007, I reported that the long-feared saturation of one the world’s primary carbon sinks had apparently started. Again in 2009, I discussed a study in Geophysical Research Letters (subs. req’d), “Sudden, considerable reduction in recent uptake of anthropogenic CO2 by the East/Japan Sea.” Most, but not all, studies have suggested the ocean was either losing its ability to absorb CO2 or soon would (see list here).
This new study, however, is different and more comprehensive than previous ones:
The analysis differs from previous studies in its scope across both time and space. One of the biggest challenges in asking how climate is affecting the ocean is simply a lack of data, McKinley says, with available information clustered along shipping lanes and other areas where scientists can take advantage of existing boat traffic. With a dearth of other sampling sites, many studies have simply extrapolated trends from limited areas to broader swaths of the ocean.
This study combines “existing data from a range of years (1981-2009), methodologies, and locations spanning most of the North Atlantic into a single time series for each of three large regions called gyres, defined by distinct physical and biological characteristics.”
[The authors] found a high degree of natural variability that often masked longer-term patterns of change and could explain why previous conclusions have disagreed. They discovered that apparent trends in ocean carbon uptake are highly dependent on exactly when and where you look – on the 10- to 15-year time scale, even overlapping time intervals sometimes suggested opposite effects.
“Because the ocean is so variable, we need at least 25 years’ worth of data to really see the effect of carbon accumulation in the atmosphere,” she says. “This is a big issue in many branches of climate science – what is natural variability, and what is climate change?”
Working with nearly three decades of data, the researchers were able to cut through the variability and identify underlying trends in the surface CO2 throughout the North Atlantic.
During the past three decades, increases in atmospheric carbon dioxide have largely been matched by corresponding increases in dissolved carbon dioxide in the seawater. The gases equilibrate across the air-water interface, influenced by how much carbon is in the atmosphere and the ocean and how much carbon dioxide the water is able to hold as determined by its water chemistry.
But the researchers found that rising temperatures are slowing the carbon absorption across a large portion of the subtropical North Atlantic. Warmer water cannot hold as much carbon dioxide, so the ocean’s carbon capacity is decreasing as it warms.
McKinley says, “this is some of the first evidence for climate damping the ocean’s ability to take up carbon from the atmosphere.”
Unfortunately, this is not some of the first evidence that amplifying feedbacks dominate the carbon cycle:
- NSIDC bombshell: Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100
- Journal of Climate: New cloud feedback results “provide support for the high end of current estimates of global climate sensitivity”
- The drying of the Northern peatlands (bogs, moors, and mires).
- The destruction of the tropical wetlands
- Decelerating growth in tropical forest trees “” thanks to accelerating carbon dioxide
- Wildfires and Climate-Driven forest destruction by pests
- The desertification-global warming feedback
Time is running out if we are to avoid levels of CO2 emissions and global warming that will rapidly take us to very high levels
Source Climate Progress Author: Joe Romm
Trenberth on Tracking Earth’s energy
Over the past 50 years, the oceans have absorbed about 90% of the total heat added to the climate system while the rest goes to melting sea and land ice, and warming the land surface and atmosphere. Because carbon dioxide concentrations have further increased since 2003 the amount of heat subsequently being accumulated should be even greater. – Kevin Trenberth Source Skeptical Science
Climate Change Drives Disease in Crucial Seaweed Species, Study Finds
Rising ocean temperatures due to global warming have already been linked to coral reef deaths, destructive storms, shifting species distributions and harmful algal blooms. Now, a team of Australian researchers is adding a new and similarly daunting concern to that list: the spread of disease in “habitat-forming” seaweeds that are critical to marine health.
Scientists fear that the widespread loss of these seaweeds could have disastrous effects on creatures that rely on them for food and protection, such as sea hares, sea urchins and dozens of fish and invertebrate species.
“Seaweeds are the ‘trees’ of coastal temperate systems,” said Peter Steinberg, a marine biologist at the University of New South Wales and director of the Sydney Institute of Marine Science, who helped lead the research that was published in the journal Global Change Biology last month.
“They provide the food and habitat for many of the other organisms that live there. Without them, these systems are radically different,” he said.
Earlier studies documented rapid decline and disease in seaweeds during the past two decades, but this analysis was the first to examine whether climate change is driving illness in habitat-forming stands that provide life to vast numbers of marine organisms.
In a 2008 study, for instance, biologists failed to locate the seaweed Phyllospora comosa along a 45-mile stretch of New South Wales, Australia — despite evidence to suggest that the species covered the coastline 50 years ago and would still be there.
A previous paper published in 1995 in the journal Science found that off Australia’s coast the amount of coralline algal pathogen, a bacteria that infects coral and other habitat-forming plants, jumped from zero to 100 percent in just one year.
The new study by Steinberg and colleagues from the University of New South Wales in Sydney focused on Delisea pulchra, a type of red algae, or seaweed, found in an area around Australia, New Zealand and Antarctica considered to be a global warming hot spot. Ocean temperatures in that region have already increased at rates well above the global average — roughly 3.6 degrees Fahrenheit in the last century, due to the strengthening of the East Australian Current system that flows south toward the South Pole.
In normal conditions, D. pulchra produces molecules known as halogenated furanones that bind to bacterial receptor sites, acting as a kind of chemical defense against infection.
Through field and lab observations, however, researchers discovered that in warmer waters — in this case, in temperatures ranging from 57 to 79 degrees Fahrenheit — the seaweeds showed higher levels of disease, or “bleaching.”
They also found that seaweeds injected with antibiotics in the hot waters experienced less disease than those in similar temperatures that were left untreated, indicating that increased bacterial activity was driving disease. Source Reuters
Ocean’s Harmful Low-Oxygen Zones Growing, Are Sensitive to Small Changes in Climate
Fluctuations in climate can drastically affect the habitability of marine ecosystems, according to a new study by UCLA scientists that examined the expansion and contraction of low-oxygen zones in the ocean. The UCLA research team, led by assistant professor of atmospheric and oceanic sciences Curtis Deutsch, used a specialized computer simulation to demonstrate for the first time that the size of low-oxygen zones created by respiring bacteria is extremely sensitive to changes in depth caused by oscillations in climate. These oxygen-depleted regions, which expand or contract depending on their depth, pose a distinct threat to marine life.
“The growth of low-oxygen regions is cause for concern because of the detrimental effects on marine populations — entire ecosystems can die off when marine life cannot escape the low-oxygen water,” said Deutsch. “There are widespread areas of the ocean where marine life has had to flee or develop very peculiar adaptations to survive in low-oxygen conditions.” The study, which was published June 9 in the online edition the journal Science and will be available in an upcoming print edition, also showed that in addition to consuming oxygen, marine bacteria are causing the depletion of nitrogen, an essential nutrient necessary for the survival of most types of algae.
“We found there is a mechanism that connects climate and its effect on oxygen to the removal of nitrogen from the ocean,” Deutsch said. “Our climate acts to change the total amount of nutrients in the ocean over the timescale of decades.” Low-oxygen zones are created by bacteria living in the deeper layers of the ocean that consume oxygen by feeding on dead algae that settle from the surface. Just as mountain climbers might feel adverse effects at high altitudes from a lack of air, marine animals that require oxygen to breathe find it difficult or impossible to live in these oxygen-depleted environments, Deutsch said.
Sea surface temperatures vary over the course of decades through a climate pattern called the Pacific Decadal Oscillation, during which small changes in depth occur for existing low-oxygen regions, Deutsch said. Low-oxygen regions that rise to warmer, shallower waters expand as bacteria become more active; regions that sink to colder, deeper waters shrink as the bacteria become more sluggish, as if placed in a refrigerator. “We have shown for the first time that these low-oxygen regions are intrinsically very sensitive to small changes in climate,” Deutsch said. “That is what makes the growth and shrinkage of these low-oxygen regions so dramatic.
“The oxygen consumed by bacteria within the deeper layers of the ocean is replaced by water circulating through the ocean,” he said. “The water is constantly stirring itself up, allowing the deeper parts to occasionally take a breath from the atmosphere.” A lack of oxygen is not the only thing fish and other marine life must contend with, according to Deutsch. When oxygen is very low, the bacteria will begin to consume nitrogen, one of the most important nutrients that sustain marine life. “Almost all algae, the very base of the food chain, use nitrogen to stay alive,” Deutsch said. “As these low-oxygen regions expand and contract, the amount of nutrients available to keep the algae alive at the surface of the ocean goes up and down.”
Understanding the causes of oxygen and nitrogen depletion in the ocean is important for determining the effect on fisheries and fish populations, he said. Deutsch and his team used a computer model of ocean circulation and biological processes that produce or consume oxygen to predict how the ocean’s oxygen distribution has changed over the past half century. The researchers tested their predictions using observations made over the last several decades, specifically targeting areas where oxygen concentration is already low, because marine life in these areas will feel the changes most quickly.
How would rising global temperatures affect these low-oxygen environments? As temperature increases, less oxygen leaves the atmosphere to dissolve in the ocean, Deutsch explained. Additionally, the shallower levels of the ocean heat up and become more buoyant, slowing the oxygen circulation to lower layers. “In the case of a global temperature increase, we expect that low-oxygen regions will grow in size, similar to what happened at the end of the last ice age 30,000 years ago,” Deutsch said. “Since these regions change greatly in size from decade to decade due to the Pacific Decadal Oscillation, more data is required before we can recognize an overall trend.
“Global warming will almost certainly influence the amount of oxygen in the ocean, but we expect it to be a slow effect that takes place over long periods of time,” he added. “There are huge changes in the volume of this low-oxygen water, but the changes oscillate in a natural cycle instead of a persistent growth as many expected. Oxygen comes and goes in the ocean in a way that is not attributable to the long-term warming of the planet. Instead, it is part of the natural rhythm of the ocean.”
“ Source Science Daily
Waiting to Inhale: Deep-Ocean Low-Oxygen Zones Spreading to Shallower Coastal Waters
Fluctuations in climate can drastically affect the habitability of marine ecosystems, according to a new study by UCLA scientists that examined the expansion and contraction of low-oxygen zones in the ocean.
The hypoxic seawater is distinct from the well-known “dead zones” that form at the mouths of the Mississippi and other rivers around the world. Those areas result from agricultural runoff, which lead to algae blooms that consume oxygen. Rather, the Pacific Northwest problem is broader and more mysterious.
Shelf waters off the Pacific Northwest extend anywhere from 30 to 80 kilometers offshore and lie beneath the California Current, one of the richest marine ecosystems in the world. Francis Chan , a senior research professor at Oregon State University, has been monitoring the area’s low-oxygen events, which normally peak in the late summer months. “Oxygen is just about the most crucial necessity for anything biological,” he says.*
Chan is one of a number of scientists alarmed at the dramatically reduced oxygen levels showing up in these waters. In fact, the Oregon Department of Fish and Wildlife put submersible vehicles off Oregon’s coast during a hypoxic event that went anoxic (oxygenless) in 2006, he says, monitoring conditions and recording numerous carcasses of sea stars, sea cucumbers, marine worms and fish.**
Lothar Stramma, a physical oceanographer at the Christian Albrechts University of Kiel in Germany and his associates describe the hypoxic problem as global in a paper accepted for publication in Deep-Sea Research , stating that tropical low-oxygen zones have expanded horizontally and vertically around the world, and that subsurface oxygen has decreased adjacent to most continental shelves. Low-oxygen zones where large ocean species cannot live have increased by close to 5.2 million square kilometers since the 1960s, the team found. Where this expansion intersects with the coastal shelf, oxygen-deprived waters are slipping up and over shelf floors, killing off creatures such as crabs, mussels and scallops. Such bottom-dwellers normally have a lot to eat in such rich ecosystems, but these species are sensitive to oxygen loss. Similarly, the anoxic ocean at the end of the Permian period (around 250 million years ago) was associated with elevated carbon dioxide and massive terrestrial and oceanic extinctions.
Lisa Levin of the Scripps Institution of Oceanography in La Jolla, Calif., says that as oxygen-starved layers move upward, large animals such as marlin, tuna and sailfish will be forced into ever-shallower waters. “That may be good for fishermen, but it also makes it a lot easier for fishermen to fish these species out of the ocean,” says Levin, who worked with Stramma on Deep-Sea Research .
Biodiversity will be the big loser as these low-oxygen zones knock out some species and promote others. Among the big winners is the Humboldt squid, which can tolerate low oxygen; it has expanded its range in the northeastern Pacific in the past 10 years, from the Gulf of California all the way to southeastern Alaska. Biologists worry about the hunting pressure the squid will put on other species.
Increases in jellyfish blooms also are likely to be part of the process. Levin encountered such blooms recently in low-oxygen environments off India’s coast, where “the jellyfish were as thick as soup,” she says. Larval fish are especially susceptible to low-oxygen ocean zones. “Larvae are really a ball of cells with a mouth and a gut. There is only so much they can do. They’re not as mobile as fish,” she says. Reproducing female crustaceans and fish may be adversely affected, as well.
Levin says that the Pacific’s deeper currents keep its waters less oxygenated than those of the Atlantic. “It’s what we call ‘old water,’ since deeper Pacific waters haven’t been at the surface in a long time,” Levin says. Stramma thinks that some of the Pacific’s oxygen problems could also result from El Niño. But climate models predict reductions in dissolved oxygen in all oceans as average global air and sea temperatures rise, and this may be the main driver of what is happening there, she says.
Chan says that lighter warm water creates a cap over the colder depths, making it less likely that deeper waters—where everything from “plankton to whale poop” sucks up oxygen—will rise to mix with the oxygenated surface. Plus, warmer water simply holds less oxygen. According to Chan, most hypoxia-intolerant species engulfed in low-oxygen waters quickly move away. “But for those whose stress response is to hunker down and wait,” he adds, “they will die.”
Source Scientific America
The development of a thick suboxic zone with high iron bioavailability – a product of dramatic changes in weathering and sedimentation patterns driven by severe global warming – may have resulted in diversification of magnetite-forming organisms, likely including eukaryotes.
- Suboxic describing a zone of water, between the oxic and anoxic zones, in which the concentration of oxygen (and sulfur) is very low. ( further see Hypoxia, Dead Zone or in general oxygen depletion)
- “The suboxic state, prevented transport of iron from the deep ocean to continental-margin settings, ending an about 1.1 billion-year-long period of banded iron formation deposition.”
- “Furthermore, as suboxic zones expand, essential nutrients are stripped from the ocean by the process of denitrification.”
- Oceanographer: Nitrous Oxide Emitting Aquatic ‘Dead Zones’ Contributing To Climate Change “When suboxic waters (oxygen essentially absent) occur at depths of less than 300 feet, the combination of high respiration rates, and the peculiarities of a process called denitrification can cause N2O production rates to be 10,000 times higher than the average for the open ocean.”
- NO2 contains an unpaired electron and is an important component of smog. N2O is a greenhouse gas with tremendous global warming potential (GWP). When compared to carbon dioxide (CO2), N2O has 310 times the ability to trap heat in the atmosphere. N2O is produced naturally in the soil during the microbial processes of nitrification and denitrification.