Alaska
Flooding that closed Alaska’s Dalton Highway also caused widespread ground sinking
The massive 2015 flooding of the Sagavanirktok River in northern Alaska had immediate impacts, including closure of the Dalton Highway for several days, but it also contributed to longer-term ground subsidence in the permafrost-rich region.
That’s the finding by assistant professor Simon Zwieback at the University of Alaska Fairbanks Geophysical Institute in a study published Sept. 27 by the journal Permafrost and Periglacial Processes.
Zwieback is the paper’s lead author. UAF scientists Mikhail Kanevskiy, Donald Walker, Vladimir Romanovsky and Franz Meyer are among the nine co-authors.
Zwieback, who also teaches at the UAF College of Natural Science and Mathematics, specializes in using space-borne remote sensing to study the Arctic.
“What previously hadn’t been known is that subsequent to the flood there were diffuse and variable changes to tundra and to this permafrost landscape,” Zwieback said. “In particular, we observed that in areas that were flooded, there were several hotspots of subsidence with subsidence exceeding three inches over a few years. And we also observed many more areas with less pronounced but still measurable sub-segments.
“We also observed a green-up and a wettening of the landscape, which was also quite variable,” he said. “All of this is important for understanding how these landscapes react to floods.”
Floodwaters began spilling onto the Dalton Highway, Alaska’s road to the North Slope, in mid-May 2015 and also reached Deadhorse airport. A pre-flood buildup of aufeis, layered ice that formed from the freezing of river water, is seen as the leading cause of the chaotic flooding. Aufeis diverted the thawing river’s water away from natural channels.
The river’s massive floodwaters exacerbated what the authors describe as a “complicated relationship” between rivers and their floodplains in regions of continuous permafrost. Human activity in the area, driven by continued expansion of the Prudhoe Bay oilfield and the presence of the Dalton Highway, has also interfered with natural drainage.
The flood may have stimulated subsidence by warming the ground, causing ground ice to melt, the authors state. Warming can be due to increased wetness, disturbance to the protective layer of organic matter or sediment deposition, allowing more heat to penetrate.
Zwieback analyzed satellite data from 2015 through 2019 to estimate ground deformation over the post-flood years.
“What we did observe from space was widespread but also quite variable subsidence,” Zwieback said.
Subsidence was most pronounced in flooded locations and was most active in the two years after the flood.
“We interpret the subsidence that we observed with remote sensing to be largely due to melting of ground ice,” Zwieback said. “Soils in the area contain substantial quantities of ice in the form of ice wedges and segregated ice, small lenses of ice as opposed to big chunks.”
Ice wedges are generally anywhere from about three to 10 feet across and about six to 10 feet deep at their narrow bottom. They form regular networks and in the study area are typically found about 30 feet apart.
“One of the main complicating factors here is that initial subsidence can trigger changes at the surface, such as ponding of water,” Zwieback said. “The surface becomes darker and warmer. And that means more thawing underneath, because you have changed the surface conditions.”
Subsidence occurred in some areas with high ice content but not in others, indicating multiple factors driving deformation. These can include organic layer disturbance and sediment deposition, which settles into the soil and drives out its insulating air pockets and allows more heat to penetrate. Researchers found fine grain sediment in the top two inches of soil plugs taken at two locations but could not conclusively state the sediment derived from the flood, despite the sample site being nearly 1,000 feet from the highway.
Researchers also found that, on average, subsiding ice-rich locations showed increases in greenness and wetness. Conversely, many ice-poor floodplains greened without deforming.
Nevertheless, the paper notes that flooding can be beneficial in the long term. It deposits sediment, which in turn allows for an increase in insulating vegetation cover and other organic matter. Over time, the active layer—a layer of soil that freezes in winter and thaws in the summer—thins. That thinning in turn allows growth of ice wedges and segregated ice. All of this increases elevation and reduces flood frequency, the authors write.
The new research is important as the Arctic comes under increasing climate stresses.
“With the Arctic becoming wetter and the flood regime changing, we need to understand how riverine landscapes respond to these changes in the rivers and the floods associated with those rivers,” Zwieback said.
More information:
Simon Zwieback et al, Disparate permafrost terrain changes after a large flood observed from space, Permafrost and Periglacial Processes (2023). DOI: 10.1002/ppp.2208
Provided by
University of Alaska Fairbanks
Citation:
Flooding that closed Alaska’s Dalton Highway also caused widespread ground sinking (2023, October 12)
retrieved 12 October 2023
from https://phys.org/news/2023-10-alaska-dalton-highway-widespread-ground.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.
Alaska
Anchorage, Alaska hit by hurricane-force winds, structures damaged across city
Associated Press
Hurricane-force winds cause widespread damage in Alaska’s largest city
Thousands of residents across Alaska’s largest city were still without power Monday, a day after a powerful storm brought hurricane-force winds that downed power lines, damaged trees, forced more than a dozen planes to divert, and caused a pedestrian bridge over a highway to partially collapse. A 132-mph (212-kph) wind gust was recorded at a mountain weather station south of Anchorage. A large low-pressure system in the Bering Sea brought the high winds, moisture and warmer than average temperatures — in the low 40s Fahrenheit (slightly over 4.4 degrees Celsius) — to Anchorage on Sunday, said National Weather Service meteorologist Tracen Knopp.
Alaska
Thousands without power in Alaska after hurricane-force winds hit
Thousands of residents in Anchorage, Alaska, faced widespread devastation and power outages Monday after hurricane-strength winds battered the city on Sunday.
Why It Matters
This latest incident comes as power outages across the United States have become a growing concern as extreme weather events increase in frequency and intensity, often leaving millions of Americans in precarious situations. Hurricanes, wildfires, ice storms and heatwaves have caused widespread disruptions, highlighting the vulnerability of aging electrical grids to severe conditions.
Prolonged outages not only hinder daily life by cutting off access to heating, cooling and essential appliances but also pose significant risks to public health, particularly for the elderly and those with medical conditions reliant on powered devices.
What To Know
The Anchorage storm, which began Sunday, delivered gusts reaching 132 mph at a mountain weather station south of the city, according to the National Weather Service. Within Anchorage itself, winds hit 75 mph, toppling trees, scattering debris and partially collapsing a pedestrian bridge over the Seward Highway, the city’s main southern thoroughfare.
At the height of the storm, 17,500 customers were without power, according to Julie Hasquet, spokesperson for Chugach Electric Association. As of Monday, roughly 5,700 homes remained offline with full restoration expected to stretch into Tuesday.
The storm’s chaos wasn’t limited to neighborhoods. Anchorage’s airport, a vital hub for passenger and cargo traffic, saw significant disruptions. Winds forced 13 aircraft, including a U.S. Air Force plane, to divert to Fairbanks, which sits nearly 360 miles away.
On the ground, emergency crews scrambled to clear bridge debris, which had obstructed traffic on the highway. However, no injuries were reported when the side fencing and roof of the bridge fell onto the four-lane divided highway on Sunday. Traffic was rerouted and crews removed the debris.
Alaska Department of Transportation spokesperson Shannon McCarthy pointed to the winds as the probable cause of the bridge failure. However, structural engineers are investigating to determine the full extent of the damage.
Meanwhile, the storm marked a rare convergence of high winds, warmer-than-average temperatures and moisture from a low-pressure system in the Bering Sea, said National Weather Service meteorologist Tracen Knopp. Anchorage saw temperatures in the low 40s Fahrenheit, unusual for mid-winter.
What People Are Saying
Alaska Department of Transportation spokesperson Shannon McCarthy said: “The winds were the leading cause, but our bridge engineers will be out there today and may be able give us a more comprehensive analysis of what happened.”
Julie Hasquet, a spokesperson for Chugach Electric Association, said some customers may not have power back on until Tuesday. She said: “When our crews show up for repairs, they don’t know what they’re going to find.”
Resident Steven Wood told Anchorage television station KTUU about how he and his family was watching the winds blow things around the yard Sunday morning when they saw their neighbor’s roof partially blow off and head right toward them.
“All of a sudden, I see the roof start to peel off, and all I can yell is, ‘Incoming! Everybody run!’” Wood said.
What Happens Next
Cleanup efforts are underway in Anchorage as the city begins recovering from the powerful storm.
This article includes reporting from The Associated Press.
Alaska
Genetic diversity in Alaska’s red king crab may provide climate change resilience
New genetic research on the Alaska red king crab reveals previously undiscovered diversity among different regions, suggesting the species is more resilient to climate change and changing ocean conditions.
Maintaining genetic diversity within and among populations is vital to ensure species are resilient to challenging conditions. Without it, a single disease or set of conditions—such as a prolonged change in ocean acidification—could drive a species to extinction.
Fortunately, new research has revealed more genetic diversity across Alaska’s red king crab populations than originally documented. This suggests that the species will be more resilient in the face of changing conditions like ocean warming. However, any efforts to enhance red king crab populations need to be careful not to affect this genetic diversity.
King crab in Alaska
Historically, the red king crab fishery was Alaska’s top shellfish fishery. It’s embedded in the culture of Alaska’s working waterfronts and king crabs have been the centerpiece of holiday feasts around the world. However, the red king crab fishery collapsed in the 1980s. Since 1983, most populations have been depressed statewide and the Gulf of Alaska fishery remains closed.
Wes Larson is co-author of the research published in Evolutionary Applications and the genetics program manager at the NOAA Alaska Fisheries Science Center. He reflects, “When it comes to understanding crab biomass declines and how to recover populations, we need to better understand population structure and local adaptation. There are a lot of concerned and invested fishermen, processors, and community members getting more engaged in these issues and it’s propelling new and innovative research.”
To dig into this need, Larson and a team of collaborators embarked on a study to generate whole genome sequencing data on red king crab in different locations across Alaska. The benefit of whole genome sequencing over previous methods is that it’s akin to reading the full story of an organism’s makeup instead of just a chapter or two. This holistic approach offers more robust analysis in order to tease apart similarities and differences between locations.
New genetics research in Alaska
Traditionally, information about commercially important species comes from fisheries-dependent data (collected on commercial fishing vessels) or independent surveys (from scientific research vessels). From these, we gather data on abundance, size, sex, reproductive status, diet, etc.
Genetics tools help to fill in the information gaps from traditional surveys, and can be used to:
- Define stock of origin
- Assess local adaptation
- Document genetic diversity and inbreeding
Whole genome sequencing builds on past methods by enhancing our ability to detect important differences between populations at finer scales.
Red king crab live in diverse environments—from coastal bays in the north, to open sea shelves in the Bering Sea. They also live in small bays and fjords fed by glacial melt in Southeast Alaska and the Gulf of Alaska. King crab in Alaska generally inhabit the following five regions:
- Southeast Alaska
- Gulf of Alaska
- Aleutian Islands
- Eastern Bering Sea
- Norton Sound / Chukchi Sea.
Previous genetic studies have hypothesized that king crab from these regions are split into three genetic groups:
- Southeast Alaska
- Gulf of Alaska / East Bering Sea
- Aleutian Islands / Norton Sound.
However, these studies used older genetic techniques, which may not provide the resolution necessary to accurately define genetic structure. The current study reinvestigated the genetic structure of the red king crab in all five regions using high-resolution data derived from whole genome sequencing.
The results of this study were revealing and informative. Scientists found substantial genetic structure within populations and genetic diversity between regions. In some cases, scientists observed this diversity between populations separated by only a few hundred kilometers.
“Crabs have pelagic larvae, so this is very surprising given the potential for ocean currents to distribute these larvae long distances,” said Larson. “However, these populations do not seem to be mixing and have become genetically isolated.”
Ultimately, the previous hypothesis of three genetic groupings was revised by this whole genome sequencing study. This updated method provided more clarity of fine-scale genetic differences than previous methods. The data indicate that there are six, possibly seven, genetically distinct populations:
- Southeast Alaska
- Gulf of Alaska
- Aleutian Islands
- Bristol Bay
- Pribilof Islands
- Norton Sound / Chukchi Sea
Data showed previously unrecognized differences between the Gulf of Alaska and East Bering Sea regions. And the East Bering Sea region is split into separate Bristol Bay and Pribilof Islands populations.
Researchers also found that the Aleutian Islands and Norton Sound/Chukchi Sea regions are unique. Data suggests that Norton Sound and Chukchi Sea may be distinct as well. However, further research is required to determine if this is the case.
Scientists attribute this genetic diversity to a combination of factors including populations deriving from different glacial refugia. These are areas that remained ice-free during the lce Age. And more recently, natural selection (genetic changes driven by adaptation) and genetic drift (genetic changes that are random) likely contributed to this diversity. The research documented evidence of local adaptation in most populations.
Fisheries management implications
The scientists’ approach to sequence the whole genome of red king crabs was a more detailed method using orders of magnitude more data than previous studies.
It also confirmed that fisheries are being managed effectively by region in Alaska. For example, crab stocks in the Gulf of Alaska, Aleutian Islands, Bristol Bay, and Pribilofs Islands regions are each managed separately. Prior to this new research, the Bristol Bay and Pribilof Islands were not found to be genetically distinct. This new understanding reinforces that we should continue to manage them separately.
Understanding population structure, and these newly discovered genetic signals of local adaptation, is also important for preventing overfishing on genetically unique populations. And it’s critical to provide information on how local adaptations influence responses to different climatic conditions.
We may find that some populations have the potential to fare better in future climate conditions that are likely as climate change progresses. Genetics can also reveal shifts in population distribution. Some shifts may already be underway in the Bering Sea as the North Pacific warms.
Finally, with the Gulf of Alaska population being depressed, scientists would expect a higher potential for inbreeding and lower genetic diversity. However, researchers found no evidence of reduced diversity, meaning genetic health did not suffer as the population declined. This foundation of genetic diversity means that genetic factors should not limit recovery.
This research also provides important data that can be used to inform broodstock selection for red king crab enhancement programs. Enhancement programs raise young crabs in hatcheries and release them into the wild to enhance the population.
Given the genetic diversity of red king crab across Alaska, it’s vital to prioritize local broodstock for enhancement before sourcing from elsewhere. This helps to keep genetic diversity intact and ensures that the genetic integrity of locally adapted populations is not jeopardized.
More information:
Carl A. St. John et al, Whole Genome Sequencing Reveals Substantial Genetic Structure and Evidence of Local Adaptation in Alaskan Red King Crab, Evolutionary Applications (2024). DOI: 10.1111/eva.70049
Provided by
NOAA Headquarters
Citation:
Genetic diversity in Alaska’s red king crab may provide climate change resilience (2025, January 13)
retrieved 13 January 2025
from https://phys.org/news/2025-01-genetic-diversity-alaska-red-king.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.
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