Tag Archives: Delta

Sydney extends lockdown for another month as coronavirus cases keep mounting

Australia’s largest city was meant to exit its five-week lockdown on July 30, but it seems it wasn’t meant to be. Citing a growing number of cases and still-low vaccination rates, local authorities have announced this Wednesday that the lockdown will be extended for one more month.

Image credits Robert Dychto.

This June, a driver for an international flight crew in Sydney contracted the coronavirus — thus plunging the city again into quarantine. After announcing 177 new cases, local authorities have announced an extension of lockdown measures. They urged those living in infection hotspots to not leave their neighborhoods, although those living alone will be allowed a “singles bubble” with another person, a move that I’m sure many interaction-starved Sydneyites will be very thankful for.

The lockdown will remain in effect until August 28, according to French news outlet AFP.

Locked Down Under — the extended cut

“I appreciate personally what we’re asking people do for the next four weeks but it is because we want to keep our community safe and want to make sure we can bounce back as quickly as possible,” New South Wales state premier Gladys Berejiklian said.

While lockdown measures remain in effect, Sydney residents can leave their homes only for exercise, essential work, to shop for necessities such as food, and for medical reasons. Local police have been issuing fines to those violating the restrictions, and Berejiklian said compliance efforts will be increased moving forward. He also asked residents to report those breaking the rules.

While Sydney is still grappling with the virus, Melbourne has just finished its fifth lockdown after beating the Delta variant of the coronavirus for the second time. Roughly eight million people in Victoria and South Australia states have also exited lockdown measures after outbreaks of the virus were deemed contained.

While Australia did move quickly against the virus in the early stages of the pandemic, it has struggled with the follow-through. It maintains a high percentage of unvaccinated citizens (roughly 76%), which left it vulnerable to the newer Delta variant. Its cities have been repeatedly going in and out of lockdown, and while Australians have been dutifully respecting these, in general, the frequent shutdowns are starting to take a toll on businesses and the general public.

Low supplies of Pfizer-BioNTech doses of the vaccine, and a wide distrust of the AstraZeneca shots are frustrating vaccination efforts. So far, Australia has officially recorded 33,000 infections and 921 COVID-related deaths.

Aerial photos show Greenland deltas growing due to climate change

While climate change and human exploitation are drowning many deltas around the world, Greenland is experiencing the opposite: warming temperatures enabled its deltas to thrive.

The land–water boundary is drawn where the high-water line (a) can be identified. Presence of snowcover (b) or icebergs (c) aids the identification process. Mouth bars (d) are included as part of the delta extent. Image credits: Bendixen et al / Nature, via Google Earth.

A team of researchers which included Mette Bendixen from the University of Copenhagen and Lars L. Iversen from the University of Colorado Boulder analyzed aerial photos from the past 75 years. They started with photos taken by the US military during World War II and compared them to what we see today.

“We examined 121 deltas by looking at historical aerial photos taken by the American army during the Second World War” Bendixen said. “We compared these with modern satellite photos. In this way, we have been able to track changes in the Greenland deltas and see what has happened over the last 75 years.”

 

Visualization of the main terrestrial and marine drivers influencing delta changes. Numbers refer to different sections. Credits: Mette Bendixen et al / Nature.

They found that the deltas had remained stable from the 1940s to 1980s, but prograded (the growth of a river delta farther out into the sea) in a warming Arctic from the 1980s to 2010s. Since human activities are virtually inexistent in the area, this effect is attributed exclusively to environmental changes — namely, global warming.

“Our study shows how climate change affects environmental processes in the Arctic landscape. As a consequence of the warmer temperatures, more sediment is transported out to the coast. At the same time, the open-water period has been extended, and the material is therefore deposited in the deltas. And in this way, the deltas are growing,” says Associate Professor Aart Kroon, corresponding author.

Climate change isn’t a uniform process. We talk about a 1 C increase in global temperatures, but that doesn’t mean that all areas of the Earth will warm by 1C. Some will warm more, some less. The Arctic areas are among those who heat up more, which makes their coastal areas (and subsequently, the deltas) highly vulnerable. Places such as Alaska, Siberia, and western Canada are suffering great coastal erosion, but the Greenland deltas are advancing into the sea. This is quite unexpected and the net impact of this process is still unclear.

The evolution of these deltas is largely governed by two factors: the freshwater runoff and associated sediment load from the catchment, and by the waves and tide from the receiving basin. As temperatures rise (especially above 0 °C), freshwater runoff increases, causing the progradation researchers found.

Journal Reference: Mette Bendixen et al. Delta progradation in Greenland driven by increasing glacial mass loss. doi:10.1038/nature23873

 

NASA’s study of the Louisiana Deltas yields fantastic images of new land being born

A NASA team showed that aircraft-mounted instruments such as radar or lidar can be used to study the development of growing deltas. Using this method they followed the evolution of the Atchafalaya basin’s coastline, where two river deltas are growing into the Gulf of Mexico, over the last 30 years.

Image credits NASA / Earth Observatory.

Louisiana is sinking

Well, it’s actually subsiding under the Gulf of Mexico’s waters at a rate of about 18 sq miles (46.6 sq km) each year. But two areas of the coast are refusing to go down — Atchafalaya River and its diversion channel, Wax Lake Outlet, each have growing deltas that gain 1.5 and 2 square miles every 11 and 8 hours respectively.

This area has been under intense observation last fall, as a team from NASA’s Jet Propulsion Laboratory in Pasadena used radar, lidar, and a host of other aircraft-mounted instruments to study the growing deltas. Their work proves that airborne observation of such environments is possible and can be accurate while collecting data helps scientists better understand how coasts respond to a rising sea level.

Deltas have been lying around ripe for observation for a long time now, so we have a pretty good understanding of the basic mechanisms that power their growth. But even NASA finds it “hard to do research in a swamp”, so there’s a lot we still don’t understand — the effect different vegetation types have on their development, or what role tides and currents play.

“These factors are usually studied using boats and instruments that have to be transported through marshy and difficult terrain,” said Christine Rains, assistant flight coordinator for the program at JPL.

“This campaign was designed to show that wetlands can also be measured with airborne remote sensing over a large area.”

Mapping the delta

The Louisiana coastline with the two growing deltas, Wax Lake and Atchafalaya, circled in red. The Mississippi River flows to the east of the delta (righ-most blue squiggly line).
Image credits USGS / NASA.

At least once a year, JPL researchers do a fly-over of the Louisiana coast to track subsidence changes and keep an eye out on the levees. So last fall, they re-tasked these flights to focus on observing the growing deltas, especially vegetation and water flow patterns. They did this because, in a delta, water doesn’t flow one way — it flows in every direction. Incoming tide pushes water into the swampy lowland and can send water back uphill.

“Water flows not only through the main channels of the rivers but also through the marshes,” explained JPL’s Marc Simard, principal investigator for the campaign.

As the tide recedes, this water carries organic-rich sediment from the marshes into the river. JPL’s project measured these flows during both rising and falling tides. It also recorded the slope of the water and mapped the riverbed — which control the rivers’ flow speeds — from its origin in the Mississippi River all the way to the ocean.

The results show that airborne monitoring of deltas is feasible, and yields high-resolution results. It also highlighted that some species of marsh vegetation are more resistant to the flow of water than others.

“We were really surprised and impressed by [the findings]. In some places, the water changes by 10 centimeters [4 inches] in an hour or two. In others, it’s only three or four centimeters [1 to one-and-a-half inches]. You can see amazing patterns in the remote sensing measurements.”

The next step is to use these measurements to improve models of how water flows through marshlands. These models form the backbone of our predictions on how coastal marshes will cope with global sea level change.

“Our models will have to catch up with the observations now,” Simard added.

The slideshow NASA put together with the deltas’ growth over the past 30 years is pure eye candy, so check it out:

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