Ocean Heat Waves Are Directly Linked to Climate Change

Ocean Heat Waves Are Directly Linked to Climate Change

SOURCE: New York Times and Science DATE: September 24, 2020 SNIP: Six years ago, a huge part of the Pacific Ocean near North America quickly warmed, reaching temperatures more than 5 degrees Fahrenheit above normal. Nicknamed “the blob,” it persisted for two years, with devastating impacts on marine life, including sea lions and salmon. The blob was a marine heat wave, the oceanic equivalent of a deadly summer atmospheric one. It was far from a solitary event: Tens of thousands have occurred in the past four decades, although most are far smaller and last for days rather than years. The largest and longest ones have occurred with increasing frequency over time. On Thursday, scientists revealed the culprit. Climate change, they said, is making severe marine heat waves much more likely. The study, published in the journal Science, looked at the blob and six other large events around the world, including one in the Northwest Atlantic in 2012. Human-caused global warming made these events at least 20 times more likely, the researchers found. “Some of these couldn’t even have occurred without climate change,” said Charlotte Laufkötter, a marine scientist at the University of Bern in Switzerland and the lead author of the study. In a world with no human-caused warming, a large marine heat wave would have had about a one-tenth of 1 percent chance of occurring in any given year — what is called a thousand-year event. But with the current rate of global warming, an ocean heat wave like that could soon have as much as a 10 percent chance of occurring, the study found. Dr. Laufkötter said...
Climate change will make world too hot for 60 per cent of fish species

Climate change will make world too hot for 60 per cent of fish species

SOURCE: New Scientist DATE: July 2, 2020 SNIP: Fish are at a far greater risk from climate change than previously thought, as researchers have shown that embryos and spawning adults are more susceptible to warming oceans. In a worst-case scenario of 5°C of global warming, up to 60 per cent of fish species around the world would be unable to cope with temperatures in their geographical range by 2100, when different stages of their lives are taken into consideration. Even if humanity meets the Paris deal’s tough goal of holding warming to 1.5°C, it would be too hot for 10 per cent of fish. Previously, we thought that just 5 per cent of fish species would struggle to cope with 5°C of global warming, but that was based on analysis of adult fish alone. Previous analysis has focused very little on life stages, but the team took into account differences between spawning and non-spawning adults, larvae and embryos. Spawners and embryos were found to cope with a much smaller gap between minimum and maximum temperatures, on average 7.2°C and 8.4°C respectively, than the 27.5°C range for adults. The greater vulnerability for embryos and reproductive adults is a “major cause for concern”, said Jennifer Sunday at McGill University in Montreal, Canada, who wasn’t involved the study, in a commentary in the journal Science. The main reason why embryos and spawners are less tolerant of warming oceans is down to their greater oxygen needs. Oxygen is more soluble in colder waters and less so in warmer ones. Unfortunately, seas are expected to warm too quickly for evolutionary adaptation. While fish can...
Study: Pace of Warming is Set to Accelerate in the Deep Ocean

Study: Pace of Warming is Set to Accelerate in the Deep Ocean

SOURCE: The Maritime Executive DATE: June 8, 2020 SNIP: A new study published in Nature Climate Change suggests that the deep ocean may not be as invulnerable to warming as once thought. By looking at the pace and horizontal movement of temperature rise over time (climate velocity), a team led by Isaac Brito-Morales of the University of Queensland predicted that life in the deep ocean will experience accelerated change in the second half of this century, even under a best-case climate action scenario. According to the study, the mesopelagic – the region between 200-1000 meters in depth – will be most affected, especially in high latitudes. This band could experience temperature changes at a rate four times higher than surface waters by the century’s end, likely resulting in “dramatic distribution changes” as deep ocean species move geographically to follow the water conditions that they prefer. Long-term fishery surveys indicate that those changes are already well under way at the surface. The study’s most concerning finding is that these deep-ocean temperature shifts will likely occur even if society takes aggressive climate action in line with the Paris Climate Accord. “The deep ocean and biodiversity below the surface of the ocean, no matter what we do, it’s going to be impacted by climate change,” Brito-Morales told CBS. The mesopelagic is the realm of the lanternfish, one of the most abundant classes of vertebrates on earth and a key food source for surface species like salmon, tuna, whales and halibut. This family of “forage fish” accounts for an estimated 65 percent of all deep sea fish biomass, and it may become a...
Climate change in deep oceans could be seven times faster by middle of century

Climate change in deep oceans could be seven times faster by middle of century

SOURCE: The Guardian DATE: May 25, 2020 SNIP: Rates of climate change in the world’s ocean depths could be seven times higher than current levels by the second half of this century even if emissions of greenhouse gases were cut dramatically, according to new research. Different global heating at different depths could have major impacts on ocean wildlife, causing disconnects as species that rely on each other for survival are forced to move. In the new research, scientists looked at a measure called climate velocity – the speed at which species would need to move to stay within their preferred temperature range as different ocean layers warm. The study, published in the journal Nature Climate Change, found different parts of the ocean would change at different rates as the extra heat from increasing levels of greenhouse gases moved through the vast ocean depths. By the second half of the century, the study found “a rapid acceleration of climate change exposure throughout the water column”. At present, the world’s heating was already causing species to shift in all layers of the ocean from the surface to more than 4km down, but at different speeds. But even under a highly optimistic scenario, where emissions fell sharply from now, the ocean’s mesopelagic layer – from 200m to 1km down – climate velocity would change from about 6km per decade to 50km by the second half of the century. But over the same period, climate velocity would halve at the surface. Even at depths of between 1,000 and 4,000 metres, climate velocity would triple current rates, even if emissions dropped...
Scientists find far higher than expected rate of underwater glacial melting

Scientists find far higher than expected rate of underwater glacial melting

SOURCE: Phys.org DATE: January 29, 2020 SNIP: Tidewater glaciers, the massive rivers of ice that end in the ocean, may be melting underwater much faster than previously thought, according to a Rutgers co-authored study that used robotic kayaks. The findings, which challenge current frameworks for analyzing ocean-glacier interactions, have implications for the rest of the world’s tidewater glaciers, whose rapid retreat is contributing to sea-level rise. The study, published in the journal Geophysical Research Letters, surveyed the ocean in front of 20-mile-long LeConte Glacier in Alaska. The seaborne robots made it possible for the first time to analyze plumes of meltwater, the water released when snow or ice melts, where glaciers meet the ocean. It is a dangerous area for ships because of ice calving—when falling slabs of ice that break from glaciers crash into the water and spawn huge waves. “With the kayaks, we found a surprising signal of melting: Layers of concentrated meltwater intruding into the ocean that reveal the critical importance of a process typically neglected when modeling or estimating melt rates,” said lead author Rebecca Jackson, a physical oceanographer and assistant professor in the Department of Marine and Coastal Sciences in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. Two kinds of underwater melting occur near glaciers. Where freshwater discharge drains at the base of a glacier (from upstream melt on the glacier’s surface), vigorous plumes result in discharge-driven melting. Away from these discharge outlets, the glacier melts directly into the ocean waters in a regime called ambient melting. The study follows one published last year in the journal Science that measured...