New Study Reveals Strong El Nino Events Cause Large Changes In Antarctic Ice Shelves

A new study published Jan. 8 in the journal Nature Geoscience reveals that strong El Nino events can cause significant ice loss in some Antarctic ice shelves while the opposite may occur during strong La Nina events.

El Niño and La Niña are two distinct phases of the El Niño/Southern Oscillation (ENSO), a naturally occurring phenomenon characterized by how water temperatures in the tropical Pacific periodically oscillate between warmer than average during El Niños and cooler during La Niñas.

The research, funded by NASA and the NASA Earth and Space Science Fellowship, provides new insights into how Antarctic ice shelves respond to variability in global ocean and atmospheric conditions.

The study was led by Fernando Paolo while a PhD graduate student and postdoc at Scripps Institution of Oceanography at the University of California San Diego. Paolo is now a postdoctoral scholar at NASA’s Jet Propulsion Laboratory. Paolo and his colleagues, including Scripps glaciologist Helen Fricker, discovered that a strong El Niño event causes ice shelves in the Amundsen Sea sector of West Antarctica to gain mass at the surface and melt from below at the same time, losing up to five times more ice from basal melting than they gain from increased snowfall. The study used satellite observations of the height of the ice shelves from 1994 to 2017.

“We’ve described for the first time the effect of El Niño/Southern Oscillation on the West Antarctic ice shelves,” Paolo said. “There have been some idealized studies using models, and even some indirect observations off the ice shelves, suggesting that El Niño might significantly affect some of these shelves, but we had no actual ice-shelf observations. Now we have presented a record of 23 years of satellite data on the West Antarctic ice shelves, confirming not only that ENSO affects them at a yearly basis, but also showing how.”

The opposing effects of El Niño on ice shelves – adding mass from snowfall but taking it away through basal melt – were at first difficult to untangle from the satellite data. “The satellites measure the height of the ice shelves, not the mass, and what we saw at first is that during strong El Niños the height of the ice shelves actually increased,” Paolo said. “I was expecting to see an overall reduction in height as a consequence of mass loss, but it turns out that height increases.”

After further analysis of the data, the scientists found that although a strong El Niño changes wind patterns in West Antarctica in a way that promotes flow of warm ocean waters towards the ice shelves to increase melting from below, it also increases snowfall particularly along the Amundsen Sea sector. The team then needed to determine the contribution of the two effects. Is the atmosphere adding more mass than the ocean is taking away or is it the other way around?

“We found out that the ocean ends up winning in terms of mass. Changes in mass, rather than height, control how the ice shelves and associated glaciers flow into the ocean,” Paolo said. While mass loss by basal melting exceeds mass gain from snowfall during strong El Niño events, the opposite appears to be true during La Niña events.

Over the entire 23-year observation period, the ice shelves in the Amundsen Sea sector of Antarctica had their height reduced by 20 centimeters (8 inches) a year, for a total of 5 meters (16 feet), mostly due to ocean melting. The intense 1997-98 El Nino increased the height of these ice shelves by more than 25 centimeters (10 inches). However, the much lighter snow contains far less water than solid ice does. When the researchers took density of snow into account, they found that ice shelves lost about five times more ice by submarine melting than they gained from new surface snowpack.

“Many people look at this ice-shelf data and will fit a straight line to the data, but we’re looking at all the wiggles that go into that linear fit, and trying to understand the processes causing them,” said Fricker, who was Paolo’s PhD adviser at the time the study was conceived. “These longer satellite records are allowing us to study processes that are driving changes in the ice shelves, improving our understanding on how the grounded ice will change,” Fricker said.

“The ice shelf response to ENSO climate variability can be used as a guide to how longer-term changes in global climate might affect ice shelves around Antarctica,” said co-author Laurie Padman, an oceanographer with Earth & Space Research, a nonprofit research company based in Seattle. “The new data set will allow us to check if our ocean models can correctly represent changes in the flow of warm water under ice shelves,” he added.

Melting of the ice shelves doesn’t directly affect sea level rise, because they’re already floating. What matters for sea-level rise is the addition of ice from land into the ocean, however it’s the ice shelves that hold off the flow of grounded ice toward the ocean.

Understanding what’s causing the changes in the ice shelves “puts us a little bit closer to knowing what’s going to happen to the grounded ice, which is what will ultimately affect sea-level rise,” Fricker said. “The holy grail of all of this work is improving sea-level rise projections,” she added.

Cyclone Lashes Southern India, Killing at Least 21

NEW DELHI — A powerful cyclone sweeping through southern India has killed at least 21 fishermen and stranded more than 90 others at sea, according to a government official in the state of Kerala.

The storm, Cyclone Ockhi, caught many fishermen off guard over the weekend after it formed quickly in the Arabian Sea and began lashing the Lakshadweep Islands and coastlines in the states of Kerala and Tamil Nadu.

On Monday afternoon, the cyclone was about 480 miles southwest of Surat, a city in Gujarat State. The storm was expected to hit the coast near Surat by Tuesday evening, and lose some of its intensity.

The extent of the damage was still unclear on Monday, but Mohammed Faizal, a member of Parliament representing Lakshadweep, said the losses from damage on the islands exceeded $77 million.

The India Meteorological Department classified it as a “very severe cyclonic storm,” a designation for tempests with wind speeds reaching 137 miles an hour.

Cyclones occur in the South Pacific and Indian Ocean; in the Atlantic and Northeast Pacific, such severe storms are called hurricanes.

“There was no forewarning,” Sekhar Lukose Kuriakose, of the Kerala State Disaster Management Authority, said by telephone. “There was no scientific means of establishing that this was going to become a cyclone.”

But fishermen, saying the government had been slow to notify people of the storm, organized protests on Saturday in Kerala and in Tamil Nadu, blocking roads and pooling resources and boats to try to locate the missing.

Speaking to the families of missing fishermen in Tamil Nadu villages, India’s defense minister, Nirmala Sitharaman, said on Sunday that the country’s navy, air force and coast guard were doing everything possible to try to find the missing fishermen.

“I speak with folded hands,” she told the crowd, in which wives of the missing fishermen wept. “We have not stopped searching for them.”

Several hundred fishermen have been rescued, the Kerala disaster management agency said. The state has announced compensation payments of about $15,000 each for the families of those who have died.

Mr. Kuriakose said that some of the missing fishermen had already been out at sea days before the cyclone formed.

Before gathering force, the storm killed at least 13 people last week in neighboring Sri Lanka, uprooting trees, forcing schools to shut and disrupting air travel.

The India Meteorological Department said the cyclone was expected to weaken gradually in the next couple of days as it moved north toward the states of Maharashtra and Gujarat.

Heavy rainfall was forecast for the area on Tuesday and officials have advised fishermen in southern Gujarat and northern Maharashtra to stay on shore.

Bali Volcano: Cyclone Dahlia Intensifies Near Indonesia – But Will Dahlia Hit Australia?

As Bali’s Mount Agung continues to erupt a tropical cyclone has been intensifying near Indonesia’s island with the latest track model revealing it could hit Australia as it travels south east.

ropical Cyclone Dahlia has intensified to a category 1 cyclone near Indonesia.

No cyclone warning has been issued for Australia and its territories but the nation’s Bureau of Meteorology warned it could increase to category 2 by Saturday morning local time.

The cyclone is currently east-northeast of the Australian territory of Christmas Island.

A statement from the bureau in Western Australia said: “Tropical Cyclone Dahlia (Category 1) was located at 1.00 AM CXT near 9.6S 108.7E, that is 345 km east northeast of Christmas Island and moving east southeast at 22 kilometres per hour.

“During Friday Tropical Cyclone Dahlia will move further east away from Christmas Island.

“While gales are not expected at Christmas Island, squally conditions and heavy rain is possible Friday morning.

“During late Friday and Saturday Dahlia will turn towards the south and intensify.

“From Sunday conditions will become less favourable for development and Dahlia is expected to begin weakening as it continues moving south.”

Indonesia’s national disaster management (BNPB) in a statement said: “Tropical cyclone Dahlia emerged.

“BMKG (the Indonesian Agency for Meteorology, Climatology and Geophysics) continues to deliver early warning of the existence of Dahlia tropical cyclone.

“On Thursday this Dahlia tropical cyclone shift was observed to the southeast with a motion speed of 13 km per hour.

“On Friday the tropical cyclone position is in the Indian Ocean south-southeast of Jakarta with maximum wind speed 95 kilometres per hour and moving towards the southeast away from Indonesia.

“It is estimated that there will be heavy rains with intensity of 50 millimetres per day and or high winds at speeds greater than or equal to 50 kilometres per hour.

“The potential for heavy rain and strong winds will occur from the west coast of Bengkulu to Lampung, south Banten, Jakarta and south west Java. Including the potential of strong winds with a force of 20 knots in the same area.

“People are encouraged to increase their vigilance against extreme weather. Heavy rain, high winds and high waves have the potential to occur.

“The threat of floods, landslides and tornadoes increases.”

It follows the devastation of tropical Cyclone Cempaka which caused landslides and flooding, killing at least 27 people.

At the time Indonesian officials warned the cyclone was pulling hazardous ash erupting from Mt Agung volcano.

Cyclone Cempaka has now dissipated, according to the BNPB.

16 Dead, 100 Missing As Cyclone Ockhi Hits India, Sri Lanka

A powerful cyclone has killed at least 16 people across India and Sri Lanka, uprooting trees and cutting power for millions amid warnings Friday that the storm would intensify.

Disaster officials said nine people were killed in India and seven in neighbouring Sri Lanka, most crushed by trees ripped up by destructive winds raging at 130 kilometres (80 miles) per hour.

Warships have been deployed to comb the southeastern coast for fishing boats missing in wild seas, India’s Defence Minister Nirmala Sitharaman said.

Another official said an estimated 100 crew were aboard the missing vessels, with fears held for their safety.

Torrential wind and rain unleashed by Cyclone Ockhi has shut down schools in Chennai, a coastal Indian city of seven million where conditions are set to worsen.

mages broadcast from southern India showed the scale of the destruction as the cyclone reached the shore, with electricity poles toppled and trees torn asunder.

Tourists in Kochi, a coastal city in the southern Kerala state, have been told to stay away from popular beaches where huge waves are pounding the shore.

Power was cut for millions in Kerala and neighbouring Tamil Nadu state as the storm made its way from Sri Lanka, with India’s meteorological department warning of worse to come.

“The system is very likely to intensify further during next 24 hours,” the department said in its update.

India’s eastern coast — including state capitals like Chennai and Bhubaneswar that are home to millions — is prone to seasonal storms that wreak immense damage between April and December.

In 1999, more than 8,000 people were killed when a cyclone battered the eastern state of Orissa.

La Niña Is Here. What Does That Mean For Our Winter?

La Niña, the cooler sibling of El Niño, is here.

The La Niña climate pattern — a natural cycle marked by cooler-than-average ocean water in the central Pacific Ocean — is one of the main drivers of weather in the U.S. and around the world, especially during the late fall, winter and early spring.

Federal government forecasters announced La Niña’s formation Thursday. The Climate Prediction Center says this year’s La Niña (translated from Spanish as “little girl”) is on the weak side, but it should still continue through the winter.

This is the second consecutive La Niña winter. Last year’s episode was unusually brief, forming in November and gone by February.

A typical La Niña winter in the U.S. brings cold and snow to the Northwest and unusually dry conditions to most of the southern tier of the U.S., according to the prediction center. The Southeast and Mid-Atlantic also tend to see warmer-than-average temperatures during a La Niña winter.

New England and the Upper Midwest into New York tend to see colder-than-average temperatures, the Weather Channel said.

Because La Niña shifts storm tracks, it often brings more snow to the Ohio and Tennessee Valleys. “Typically La Niña is not a big snow year in the mid-Atlantic,” said Mike Halpert, deputy director of the Climate Prediction Center. “You have a better chance up in New England.”

Texas A&M University agricultural economist Bruce McCarl said La Niña years are often bad for agriculture in Texas and the surrounding region. U.S. production of most crops — except corn — generally goes down in La Niña years, according to research by McCarl.

Globally, La Niña often brings heavy rainfall to Indonesia, the Philippines, northern Australia and southern Africa.

The entire natural climate cycle is officially known as the El Niño – Southern Oscillation (ENSO), a see-saw dance of warmer and cooler seawater in the central Pacific Ocean

2017 Hurricane Season Produces Most Reported Tornadoes in Nearly a Decade

2017 is now the fourth hurricane season since 1995 with tropical storms or hurricanes that produced more than 100 tornadoes. Only the 2005 (317), 2004 (238) and 2008 (139) hurricane seasons produced more tornadoes.

Most of the tornadoes associated with tropical cyclones develop in bands of thunderstorms and intense showers outside the eyewall about 50 to 250 miles from the hurricane or tropical storm center.

The majority of tornadoes spawned by tropical storms and hurricanes are short-lived and of the weaker EF0 or EF1 variety, but some can reach EF2 or EF3 intensity. Because of their short-lived nature, sometimes they can strike with little or no advance warning.

Hurricane Ivan in 2004 is the most prolific tornado-producing hurricane in U.S. weather history. A total of 120 tornadoes struck nine states from Florida to Pennsylvania in a three-day period.

But not all hurricanes generate a large number of tornadoes, as 2016’s Hurricane Matthew illustrated. Matthew only produced two EF0-rated tornadoes since the eastern side of the hurricane, which is favored for tornado development, remained offshore.

Typhoon Saola Downgraded But Expected To Drench Pacific Coastal Areas As It Nears Hokkaido

Typhoon Saola was churning along the Pacific coast of Honshu toward Hokkaido Monday morning, with the Meteorological Agency warning the storm was bound to release more heavy rain to northern regions.

But the season’s 22nd typhoon was weakened into a low-pressure system off Japan’s northeastern coastline early Monday morning after passing south of the Kanto region, the agency said.

The typhoon was moving off the Sanriku coast of Iwate Prefecture as of 12:50 a.m. and had an atmospheric pressure reading of 980 hectopascals. It was heading northeast at a speed of 100 kph, the weather agency said.

The agency warned of strong winds, river flooding caused by heavy rain, and mudslides.

On Sunday, the typhoon brought heavy rain to many regions. The cities of Miyazaki and Nichinan, in Miyazaki Prefecture, saw a record amount of rainfall in 24 hours, with more than 400 mm by Sunday morning.

In Miyazaki and Oita prefectures, two women, one aged 79 yand the other 86, fell down and broke their legs.

The agency said the Tokai region would get up to 180 mm of rain over a 24-hour period ending at noon on Monday, 150 mm in the Hokuriku and Kanto-Koshin regions, and 100 mm in the Tohoku region.

The typhoon disturbed transportation networks, forcing operators to cancel some services.

According to an NHK report, a total of 86 flights, mostly in Kyushu and Okinawa, were canceled Sunday.

Kyushu Railway Co. halted some operations on sections of the Nippo and Nichinan lines, while East Japan Railway Co. suspended the Sunrise Izumo limited express sleeper service and other services.

The typhoon also disrupted various events, including the 37th Oita International Wheelchair Marathon in Oita Prefecture. The race was due to start Sunday morning but was canceled, its organizers said.

Saola follows in the wake of Typhoon Lan, which battered much of the country with heavy rain and strong winds just a week ago. Lan killed seven people and injured nearly 100 others, causing floods, mudslides and traffic disruptions.

When Lan hit, it also disrupted ballot counting for the Oct. 22 House of Representatives election.

A number of municipalities had issued evacuation advisories to residents and regional election boards had to forgo vote-counting until the ballots could be delivered. On Oct. 23, Lan made landfall in Shizuoka Prefecture and ran over Tokyo, triggering floods, mudslides and traffic disruptions.