#Snowpack/#Drought news: “It’s getting warmer and we’re seeing less precipitation in the wintertime” — Jeff Derry

Westwide SNOTEL basin-filled map April 12, 2018 via the NRCS.

From The Aspen Times (Brent Gardner-Smith):

The members of the Rio Grande Basin roundtable got a disheartening report this week about this year’s snowpack and likely runoff in the Rio Grande River basin, as well as an update on a 30-year warming and drying trend.

“We’re going to have low stream flows,” Craig Cotten, the division engineer for the Colorado Division of Water Resources in the basin, told the roundtable Tuesday at its monthly meeting in Alamosa, just a few blocks from the river. “I’m sure we’re going to dry up the Conejos (River) and maybe the Rio Grande, in some spots.”

Cotten shared snowpack data taken from snow telemetry, or SNOTEL sites, around Colorado, which measure the amount, and weight, of the snowpack at specific locations around the state.

The data this week showed a decline in snowpack from north to south in Colorado.

The North Platte River basin, to the northeast of Steamboat Springs, was at 102 percent of the median level for that date.

The South Platte River basin, which includes Denver, was at 93 percent.

The Yampa and White river basins, north of Interstate-70, were at 89 percent.

The Colorado River basin, which includes Glenwood Springs and Aspen, was at 86 percent.

The Gunnison River basin, further south, was at 60 percent.

The Rio Grande River basin was at 40 percent.

And the San Miguel, Dolores, Animas and San Juan river basin, in the southwest corner of the state, was at 39 percent.

So while water managers and river users in the northern and eastern part of the state may have more water than their southern counterparts, it’s a bit like passengers in a lifeboat having more drinking water in their end of the boat than the passengers in the other end — it’s nothing to gloat about.

Jeff Derry is the executive director of the Center for Snow and Avalanche Studies in Silverton, which studies the “dust on snow” phenomenon and how it affects the state’s snowpack.

Derry focuses on information from “snow course” sites, in addition to SNOTEL sites, as the snow course sites measure the snow water equivalent, or moisture levels in the snow, across broader landscape areas and have often done so over longer periods of time than SNOTEL sites.

He showed the roundtable graphs that indicate the snowpack in the southern part of the state, as of April 1, was tracking right at the same level as the very dry years of 1977 and 2002, while the whole of the state, on average, was tracking just above those drastically low years.

The avalanche center’s website has a graph that takes the average of 81 snow course sites across Colorado.

“Water year 2018 is comparable to 1966, 1981, 1999, 2004, (and) 2012,” Derry wrote. “We are faring just very slightly better than 1977 and 2002.”

Derry’s graphs also included long-term trend lines dating back 30 to 80 years, which clearly indicate Colorado’s snowpack has been shrinking and temperatures have been rising, especially on the colder end of the spectrum, meaning the lowest temperatures in winter are not as low as they used to be, especially over the past 30 years.

“It’s getting warmer and we’re seeing less precipitation in the wintertime,” Derry told the roundtable members.

Aspen Journalism is covering rivers and water in collaboration with The Aspen Times. More at http://www.aspenjournalism.org.

From The Grand Junction Daily Sentinel (Dennis Webb):

State weather experts say the snowpack in the Gunnison River Basin and farther south will likely melt out a month earlier than normal this spring even as snow levels farther north continue to fare better, thanks in part to a recent storm.

“Things are getting better in the areas that are just slightly below normal, and still getting worse in the areas that are way below normal,” Peter Goble, climatologist and drought specialist at the Colorado Climate Center, said Tuesday in a webinar on drought conditions.

The update came at a time when snowpack levels in river basins typically reach their peaks and spring runoff begins. Assistant State Climatologist Becky Bolinger said the San Juan River Basin area in southwest Colorado already likely has peaked at 50 percent of normal seasonal peak accumulation, and the Gunnison basin, which is at 58 percent of seasonal median peak, also may have peaked…

She said the same goes for the San Juan area, while Goble said the Upper Rio Grande Basin is melting out even faster. He said he recently visited southern Colorado and the snowpack looked “heartbreaking” in the San Juan area and “pretty miserable” in the Sangre de Cristo mountains.

Many snow-measurement sites are recording the lowest snowpacks on record in southern Colorado. Sites on Grand Mesa are showing snowpacks at less than half of average, and at or near record low levels.

Meanwhile, the storm that hit northern Colorado watersheds several days ago brought up to 2½ feet of snow, the Colorado Climate Center says. In terms of water content, Bolinger said the storm brought two to three inches of precipitation to some higher-elevation areas and more widespread precipitation ranging from a half-inch to an inch.

Yampa River Basin snowpack is at 80 percent of seasonal peak levels, and the Upper Colorado River Basin in Colorado is at 77 percent of peak. Bolinger hopes to see more accumulation in the Upper Colorado Basin, but she said peak accumulation there usually arrives by mid-April…

Colorado’s statewide snowpack was at 72 percent of median Tuesday, up from 68 percent at the start of the month. The snowpack is now where it stood March 1 before falling due to March precipitation that was only 65 percent of normal, according to the Natural Resources Conservation Service.

Some streams already are running below average levels, and the NRCS said last week that spring and summer streamflows in Colorado will be between 30 and 70 percent of normal.

It said the Gunnison River at Grand Junction is forecast to have only 33 percent of average streamflow, and the Colorado River at Cameo is expected to flow at 64 percent of average. The Gunnison’s flow will be affected by the U.S. Bureau of Reclamation’s efforts to hold back as much water as it can in Blue Mesa Reservoir, which it expects will fill to about three-quarters of capacity.

Goble said while it doesn’t appear that McPhee Reservoir in southwest Colorado will fill this year, it sounds like farmers in the Four Corners area are being promised their full irrigation allotment. While the reservoir may be drawn down some this year, “we’re not in miserable shape there,” he said.

Reservoir storage that is at 114 percent of average statewide and is above average even in southwestern Colorado continues to ease the sting of this winter’s poor snowfall. Bolinger said she’s not hearing a huge concern from water providers this year…

She said areas that rely only on streamflow will have more of a concern, as will growers of some dryland crops.

She said water officials will be watching how much reservoir levels can be built up this spring. Southern reservoirs aren’t likely to be able to store additional water due to low runoff and increased drawing down due to drought. That will mean that next winter a more normal snowpack will be needed to help those reservoir levels recover.

If next winter is similar to this year, “that’s when we’re really looking at having to make some hard decisions … and really feeling the effects of drought,” she said.

From The Vail Daily (Scott Miller):

A heavy storm last weekend did more than put smiles on the faces of local powder hounds. That storm, by itself, put down 18 percent of Vail Mountain’s current snowpack.

According to the vail.com website, Vail Mountain has received 23 inches of snow in the past seven days, virtually all of it from that weekend storm.

Elsewhere on Vail Mountain, the U.S. Department of Agriculture’s snow-measurement site recorded 14.6 inches of “snow water equivalent,” enough to finally surpass the record-low snow season of 2011-12.

Still, the site is recording a total well below the 30-year median — just 70 percent.

The news is better at the measurement sites at Copper Mountain and Fremont Pass. Those sites are the closest ones to the headwaters of Gore Creek and the Eagle River, respectively.

At Copper Mountain, the measurement site is at 95 percent of the 30-year average. At Fremont Pass, the total is 111 percent of average…

Last weekend’s storms were still more than welcome. [Peter] Goble called the storm a “game-changer” in terms of snowpack. While snowpack is still well below normal through most of the state, Goble said the next drought map from his office will have some changes. Locally, some of the areas in Eagle County will drop back one level in its classification. Areas that most recently were in “severe” drought will drop back to “moderate,” while the area around Vail may revert to the lowest classification, “abnormally dry.”

From The Craig Daily Press (Eleanor C. Hasenbeck):

As of April 10, snowpack in the Yampa and White River Basin was at 89 percent of normal, which is nearly the highest it’s been this water year, said National Weather Service meteorologist Jeff Colton. To the north, Wyoming’s Green River Basin is at 91 percent of median.

The Stagecoach, Elkhead and Yamcolo Reservoirs are expected to fill or nearly fill…

Now, timing is key. Availability of water through the course of the season is dependent on the timing and amount of spring precipitation and melting snowpack.

Currently, water managers are bypassing water from rain and snowmelt through Stagecoach Reservoir, because it can’t be filled until the ice on top of the water has melted; ice flowing through the dam’s spillway would damage the infrastructure of the reservoir.

On the Yampa, managers don’t want to see too much too soon. Gray said the Yampa typically hits the high water mark around June 1 in Moffat County…

As long as the area gets more spring moisture — and warm temperatures don’t melt snowpack in the Park Mountains too early — Gray said irrigation in the area is expected to be “a little short,” but water is not anticipated to be as scarce as it appeared it might be earlier this year…

For now, Northwest Colorado still faces drought conditions, according to the United States Drought Monitor. The eastern half of the county and a sliver in the northwest corner of the county are in abnormally dry conditions. Most of western Moffat County is in a moderate drought, while the Dinosaur and Massadona areas face severe drought conditions.

Gila River watershed. Graphic credit: Wikimedia

From the Arizona Department of Natural Resources:

Not without good reason, the nation’s media have been focusing on the dramatically thin snowpack of the Upper Colorado River Basin, which portends a meager amount of runoff into the Colorado River system.

As of April 2, the basin snowpack stood at just 72 percent of normal, heralding a runoff season that may be the sixth driest in the 55 years that Glen Canyon Dam and Lake Powell have been in place to capture the runoff.

On average, the in-flow into Lake Powell is 7.1 million acre-feet per season. Although the figure may change, this year’s projection currently stands at less than half that amount – 3.1 million acre-feet.

Bad news? Oh, yes. But where Arizona’s renewable water supplies are concerned, the 2018 story gets still worse. As opposed to the Colorado River system, the in-state river systems are setting records.

The Salt River Project is reporting that, according to provisional data for runoff in the Salt and Verde reservoir systems, the January – March runoff totals are “the lowest amounts on record dating back to 1913.”

Water Year precipitation for the State’s two major watersheds (Oct. 1 – Mar. 31) stood at just 2.88 inches, a figure that unsurprisingly graded out as “Well Below Normal.”

As a result, runoff in the watershed has been extremely poor. SRP data indicate that runoff into the Salt and Verde reservoirs in March stood at just 14 percent of median – the second-lowest amount on record.

In the wake of a December – February snowpack season that produced next to nothing in the two Arizona watersheds, three small storms after mid-March produced a snow-water equivalent of just 22,000 acre-feet, most of it at the highest elevations of the region.

Overall, total watershed streamflow this runoff season (January -May) is forecast to be near the lowest on record, which stood at 106,000 acre-feet in 2002.

SNOTEL data produced by the Natural Resource Conservation Service depict snowpack values as high as 40 percent of normal and as low as zero percent of normal.

If you seek to frolic in the snow in Arizona, you’ll be hard-pressed to find white stuff for your skis: According to satellite data, just 0.3 percent of the watershed had snow coverage as of April 1.

If winter in Arizona proved dry, early spring doesn’t hold out much hope for moisture here, either. Reports indicate that Arizona should anticipate warmer, drier weather through the first half of April, at least.

From The Mohave Daily News:

Forty-five percent of Arizona is now in extreme drought according to the Arizona Drought Monitoring Technical Committee.

The committee released a report last week showing statewide drought conditions worsened during March. The continued dryness led to drought declarations on the Navajo Nation and in Yuma County.

Though a series of weak storms passed through Arizona, they left only insignificant snow, according to the report. The southern half of the state remained dry and northern Arizona received only scattered light precipitation. The committee noted rangeland conditions are very poor with little forage, and water hauling for both livestock and wildlife has begun in many parts of the state…

U.S. Bureau of Reclamation reports as of Tuesday showed Lake Powell is 56 percent full and Lake Mead is at 41 percent, with an 1,087 foot elevation, roughly 12 feet above the 1,075 elevation that would trigger automatic first tier shortages for Central Arizona Project deliveries.

BuRec does not anticipate any level of shortage in Lake Mead for 2018, but increased the probability of shortage in 2019 from 15 percent in August 2017 to 17 percent probability now. BuRec’s Colorado River Simulation System model also increased the probability of shortage in 2020 by 7 percent, in 2021 by 13 percent and in 2022 by 11 percent.

Worse, ADWR officials said, in-state river systems are historically low; provisional data for runoff in the Salt and Verde reservoir systems show the January through March runoff totals are “the lowest amounts on record dating back to 1913.”

#Drought news: D2 (Severe Drought) increased in east-central #Colorado, D3 (Extreme Drought) now covered SE #Utah, SW Colorado

Click here to go to the US Drought Monitor website. Here’s an excerpt:

Summary

A series of storms systems with varying amounts of precipitation swept across most of the lower 48 States this week, including the Far West which was mostly dry last week. After a very dry February, normally one of the wettest months of the year in California, repeated storms have brought welcome precipitation to most of the state, gradually increasing WYTD precipitation and Sierra snows closer to normal. Decent precipitation (2-6 inches, locally to 10 inches) also fell on western Oregon and Washington and in the Cascades. In the Southwest, however, storms have generally bypassed this region this winter (and this week), and after a disappointing 2017 summer monsoon, drought conditions expanded and worsened. To the east, light to moderate precipitation fell on the northern and central Rockies, north-central Plains, the western Corn Belt, and most locations in the eastern third of the Nation. The greatest amounts (1.5-4 inches) fell on the lower Mississippi and eastern Ohio Valleys, eastern Carolinas, and north-central Florida. Subnormal temperatures prevailed across much of the contiguous U.S. east of the Rockies (except Florida), and averaged above-normal in the Southwest. Showery weather continued across Hawaii and Puerto Rico (where no drought existed) while drier weather occurred across Alaska…

South

Like last week (and many other recent weeks), significant precipitation fell mainly on non-drought areas of Arkansas, Mississippi, Tennessee, Louisiana, and eastern sections of Oklahoma and Texas, and bypassed the drought in western Texas and Oklahoma. With the early October rains falling out of the most recent 6-month period, SPIs plunged to D3 and D4 levels across northern new Mexico, northern Texas, western Oklahoma, southern Colorado, and southwest Kansas. The early October rains seemed like a long-faded memory as most non-irrigated winter wheat fields and pastures in the panhandles of Texas and Oklahoma were in very poor or dead condition. According to NASS/USDA April 8 reports, 61%, 57%, 44%, and 19% of Texas, Oklahoma, Kansas, and Colorado winter wheat was in poor or very poor condition, respectively, and 41%, 40%, 37%, and 26% of Colorado, New Mexico, Oklahoma, and Texas pastures and ranges were in similar condition (Kansas N/A). In parts of northern Texas, soils were dry down to 1-3 feet, whereas other locations were dry in the upper 12-18 inches, and Level 2 water restrictions were in place for Canyon, TX. While some areas benefited from the early October rains and were kept at D3, D4 was expanded into northeastern New Mexico, northern Texas,, western Oklahoma, and southwestern Kansas where the impacts matched the indices. In contrast, with additional light rains in central and southern Texas, plus heavier rains from last week, minor adjustments (mostly improvements) were made to the D0-D2 areas, except for some D2 expansion north of Del Rio that missed out on the rains during the past 2 weeks. In southern Louisiana, light showers (0.5-1.5 inches) fell on the D0 area, but the heaviest rains fell north and south (offshore), thus no changes were made…

High Plains

Another week of light precipitation (snow) and subnormal temperatures enveloped the northern Plains, with some heavier amounts (0.5-1 inch) falling on northern and eastern South Dakota and the Black Hills. In east-central South Dakota, 4-8 inches of snow fell from Aberdeen southeastward past Watertown, and with this moisture, a slight D0 removal was made where indices out to 6-months were wet, and since this D0 was short-term, it was easier to justify its removal; however, the D0 was kept where frost depths were deeper (down to 2-4 feet) in the northeast. After several weeks of gradual improvements in eastern Montana and the western Dakotas, no changes were made this week as precipitation was lighter. In northern Colorado, some decent precipitation fell on the central Rockies, finally allowing for some small 1-category improvements in northwestern and north-central sections of the state as WYTD indicators climbed above various D0-D2 percentile thresholds. Farther south, similar to other south-central Plain states, Kansas saw little or no precipitation (less than 0.25 inches) as not only short-term indices (6-months or less) but also longer-term tools (9- and 12-months) indicated drier conditions than depicted. Accordingly, the D4, D3, D2, and D1 borders were slightly extended northward to reflect the severe conditions and growing deficits (8-14 inches at 12-months in central Kansas). The April 8 NASS/USDA winter wheat rating for Kansas stood at 44% in poor or very poor condition, with Kansas the top state for winter wheat production. No changes were made between the border of Nebraska and Kansas as a few extra snow events this year across this area have contributed enough moisture to prevent deterioration, at least for now…

West

After experiencing rather tranquil weather last week, stormy weather returned to the Far West as has thankfully been the case since early March – after a near-record dry February (third driest February in California since 1895, according to NCEI). With the continued train of spring storms providing badly-needed moisture to California, additional improvements were made to areas with the greatest weekly totals (3-8 inches) that have also neared their normal WYTD precipitation. With most major reservoirs above their April 10 historic average and stream flows nearing 7-day record highs due to the combination of heavy rains and some snow melt, D0 was removed from northern and central coastal and Sierra Nevada locations, while D1 was improved to D0 near and south of Fresno to near Bakersfield. Although WYTD deficits remained, this latest storm caused flooding, and coupled with last winter’s surplus precipitation, conditions have improved with the spring storms. April 10 snow water equivalents (SWE), however, remained below normal, with northern (36%), central (51%), and southern (39%) Sierras seeing some snow melt from lower elevation rains. Statewide, the SWE summary stood at 11.7 inches, or 43% of normal for April 10. Likewise, additional precipitation over northeastern Nevada (D0 to nothing hole) and along the Nevada-Oregon border (D1 to D0) warranted a 1-category improvement.

In contrast, another week of disappointing dry and warm weather in the Southwest led to additional deterioration. In southern California, after reassessing reservoir conditions at Lakes Cachuma, Casitas, and Piru in Santa Barbara and Ventura counties, the earlier March rains did little to increase their levels, thus D2 was returned to those counties. While higher terrains in California’s Owen Valley and eastward into Nevada did fairly well with March storms, the lower elevations did not, and when combined with a poor fall and winter, D1conditions were expanded into southern Nevada. In addition, D2 was increased in east-central Colorado with 6-month SPIs between -1 and -2.5. D3 now covered southeastern Utah, southwest Colorado, and central New Mexico as another dry and warm week dropped WYTD basin average precipitation to 50, 43, and 19-27% of normal, respectively, while the mountain snows have completely melted in eastern Arizona and most of New Mexico (0% SWE). In southeastern Utah and northeastern Arizona, D4 areas were added to reflect both the poor winter conditions and the weak and early ending summer monsoon of last year (12-month indices at D4). In northeastern New Mexico, D4 was extended into Union and Colfax counties as near- or record dry 6-month precipitation, above-normal temperatures, low humidity, and strong winds combined to produce very poor irrigated winter wheat, along with bare, dead, or very poor pasture and range conditions according to field observations…

Looking Ahead

During April 12-16, 2018, more precipitation is expected for the Pacific Northwest southward into northern California and the Sierra Nevada, and then eastward across the northern sections of the Rockies and Plains. Widespread moderate precipitation (0.5-2 inches) is anticipated for most of the eastern third of the Nation, with the greatest totals (2-4 inches) targeting the lower Mississippi and Tennessee Valleys, the north-central Great Plains, and the upper Mississippi Valley and Great Lakes region. Heavy snow should blanket the north-central Plains and upper Midwest. Unfortunately, the Southwest and southern half of the Plains is expected to remain dry. Temperatures should average below normal across much of the lower 48 States, especially in the northern Plains and upper Midwest, while the mid-Atlantic and Ohio Valley experience unseasonable warmth for a change.

For the ensuing 5 days (April 17-21), odds favor above-median precipitation across much of the West, Rockies, and Plains, except near to below-median totals in southern Arizona and most of New Mexico and Texas. The upper and middle Mississippi Valleys, Great Lakes region, northern New England, and southern half of Alaska also favor above-median precipitation chances, while sub-median totals are likely for the Southeast, Appalachians, and mid-Atlantic. Subnormal temperatures are a good bet across much of the lower 48 States except in the southern Plains and extreme southern Florida, with Alaska tilting toward above-normal readings in the west and below-normal in the east.

Drug waste clogs rivers around the world, scientists say: “We need a substantial reduction in consumption” — Francesco Bregoli

The White-Rumped Vulture (Gyps bengalensis) is an Old World vulture native to South and Southeast Asia. It has been listed as Critically Endangered on the IUCN Red List since 2000, as the population severely declined. White-rumped vultures die of renal failure caused by diclofenac poisoning. In the 1980s, the global population was estimated at several million individuals, and it was thought to be “the most abundant large bird of prey in the world”. As of 2016, the global population was estimated at less than 10,000 mature individuals. Photo credit: Wikimedia

From The Guardian:

Large numbers of pharmaceuticals found at levels dangerous for wildlife and the environment

River systems around the world are coursing with over-the-counter and prescription drugs waste which harms the environment, researchers have found.

If trends persist, the amount of pharmaceutical effluence leaching into waterways could increase by two-thirds before 2050, scientists told the European Geosciences Union conference in Vienna on Tuesday.

“A large part of the freshwater ecosystems is potentially endangered by the high concentration of pharmaceuticals,” said Francesco Bregoli, a researcher at the IHE Delft Institute for Water Education in the Netherlands, and leader of an international team that developed a method for tracking drug pollution “hotspots”.

A large number of drugs – analgesics, antibiotics, anti-platelet agents, hormones, psychiatric drugs, antihistamines – have been found at levels dangerous for wildlife.

Endocrine disruptors, for example, have induced sex changes in fish and amphibians.

Bregoli and his team used a common anti-inflammation drug, diclofenac, as a proxy to estimate the presence and spread of other medications in freshwater ecosystems.

Both the European Union and the US Environmental Protection Agency have identified diclofenac as an environmental threat. Veterinary use of it has driven a sub-species of vultures on the Indian subcontinent to the brink of extinction.

More than 10,000km of rivers around the world have concentrations of diclofenac above the EU “watch list” limit of 100 nanograms a litre, the new research found.

“Diclofenac emissions are similar to any of thousands of pharmaceuticals and personal care products,” said Bregoli.

Global consumption of diclofenac tops 2,400 tonnes a year. Several hundred tonnes remain in human waste, and only a small fraction – about 7% – of that is filtered out by treatment plants.

Another 20% is absorbed by ecosystems, and the rest go into oceans.

Bregoli and his team developed a computer model to predict current and future pharma pollution based on criteria such as population densities, sewage systems and drugs sales.

They compared the results to data gathered from 1,400 spot measurements of diclofenac toxicity taken from around the world. Most of the data points were in Europe and North America.

Pollution levels are likely to be substantially higher in much of Latin America, Africa and Asia where less than a quarter of waste water is treated, and with technology unable to filter out most pharmaceuticals.

Technology alone cannot solve the problem, said Bregoli.

“We need a substantial reduction in consumption,” he said.

In other research presented at the conference, scientists found that the rapid expansion of sewage systems in large urban areas has sharply raised river pollution because much of it is not adequately treated.

“In 2000, sewage was a source of pollution in about 50% of the rivers in the world,” said Maryna Strokal, a scientist at Wageningen University and Research in the Netherlands.

“By 2010, sewage was a source of pollution in almost all rivers worldwide.”

Antibiotics and chemicals waste is also driving the evolution of drug-resistant bacteria, UN Environment warned in a study in December.

Between 70% and 80% of all antibiotics consumed by humans and farm animals – thousands of tonnes – find their way into natural environments, it said.

Stronger evidence for a weaker Atlantic overturning: “We’re finally detecting that pattern” — Stefan Rahmstorf #ActOnClimate

Observed temperature change since 1870. Graphic credit: Levke Caesar/Potsdam Institute for Climate Impact Research

From The Washington Post (Chris Mooney):

The Atlantic Ocean circulation that carries warmth into the Northern Hemisphere’s high latitudes is slowing down because of climate change, a team of scientists asserted Wednesday, suggesting one of the most feared consequences is already coming to pass.

The Atlantic meridional overturning circulation has declined in strength by 15 percent since the mid-20th century to a “new record low,” the scientists conclude in a peer-reviewed study published in the journal Nature. That’s a decrease of 3 million cubic meters of water per second, the equivalent of nearly 15 Amazon rivers.

The AMOC brings warm water from the equator up toward the Atlantic’s northern reaches and cold water back down through the deep ocean. The current is partly why Western Europe enjoys temperate weather, and meteorologists are linking changes in North Atlantic Ocean temperatures to recent summer heat waves.

The circulation is also critical for fisheries off the U.S. Atlantic coast, a key part of New England’s economy that have seen changes in recent years, with the cod fishery collapsing as lobster populations have boomed off the Maine coast.

Some of the AMOC’s disruption may be driven by the melting ice sheet of Greenland, another consequence of climate change that is altering the region’s water composition and interrupts the natural processes.

This is “something that climate models have predicted for a long time, but we weren’t sure it was really happening. I think it is happening,” said one of the study’s authors, Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany. “And I think it’s bad news.”

But the full role of climate change in the slowing ocean current is not fully understood, and another study released Wednesday drew somewhat different conclusions.

This study, which was also published in the journal Nature, found that the AMOC has slowed over the past 150 years and similarly found that it is now weaker than at any time in more than a millennium.

“The last 100 years has been its lowest point for the last few thousand years,” said Jon Robson, a researcher at the University of Reading and one of the study’s authors. (The study’s lead author was David Thornalley of the University College London.)

The two studies have their differences: The second suggests the slowdown probably began for natural reasons around the time of the Industrial Revolution in 1850, rather than being spurred by human-caused climate change, which fully kicked in later.

But like the first study, the second finds that the circulation has remained weak, or even weakened further, through the present era of warming.

Sharp changes off the coast of Maine

The authors of the first study believe the shift in the circulation may already having a big impact along the U.S. coastline.

“Of all the U.S. waters, this region has definitely warmed the fastest in the last decade,” said Vincent Saba, a marine biologist at the National Oceanic and Atmospheric Administration and one of its co-authors.

And that has had major effects on fisheries. The Gulf of Maine, for instance, has seen a giant boom in the local lobster industry and crash of the cod fishery.

“A lot of these changes are happening relatively fast, and our fisheries management is unable to keep up,” Saba said. “We’re trying to figure out how to deal with some of these species shifts that we’re seeing.”

It’s not just fisheries: If the slowdown trend continues, it is expected to drive strong sea-level rise against the Eastern Seaboard. Previous research has already shown that from 2009 to 2010, sea level in the region suddenly shot up five inches, thanks in part to a brief slowdown of the circulation.

This occurs, Rahmstorf explains, because the northward flow of the Gulf Stream pushes waters to its right — which means that the ocean piles up against the coast of Europe. But as the current weakens, some of the water flows back toward the United States’ East Coast instead.

As for the future, Rahmstorf predicts the circulation will only weaken further as climate change advances. It may not be slow and steady: There is great fear that there may be a “tipping point” where the circulation comes to an abrupt halt.

This is one of the most infamous scenarios for abrupt climate change, as it is known: Studies from the planet’s history suggest that such a sudden change in the North Atlantic has occurred many times in Earth’s past, perhaps as recently as about 13,000 years ago. But it’s not clear how close the tipping point might be.

“I think in the long run … Greenland will start melting even faster, so I think the long-term prospect for that ocean circulation system is that it will weaken further,” Rahmstorf said. “And I think that’s going to affect all of us, basically, in a negative way.”