College of Alaska Fairbanks researchers have developed a method to make use of radar to detect open water zones and different modifications in Alaska’s frozen rivers within the early winter. The strategy will be automated to offer present hazard maps and is relevant throughout the Arctic and sub-Arctic.
Many Alaskans, particularly in rural elements of the state, use rivers as wintertime ice highways to journey between communities or for recreation, looking and fishing. Open water zones in river ice will be harmful.
The brand new methodology is detailed in a paper printed March 13 within the journal Distant Sensing of Setting.
Distant sensing scientist Melanie Engram of the Water and Environmental Analysis Middle on the UAF Institute of Northern Engineering led the analysis.
Co-authors embrace Franz Meyer of the UAF Geophysical Institute; Dana Brown, Sarah Clement and Katie Spellman of the UAF Worldwide Arctic Analysis Middle; and Allen Bondurant, Laura Oxtoby and Christopher Arp of the Water and Environmental Analysis Middle.
“Arctic warming has modified the methods rivers freeze and has impacted rural winter river journey resulting from later freeze-ups, mid-winter open water zones and earlier breakups,” the authors write.
Prior analysis by others targeted on only one or two river reaches in Canada and temperate climates in Lithuania.
Engram and her UAF colleagues used artificial aperture radar knowledge from 12 reaches on eight Alaska rivers to create a river ice classification system that can be utilized in northern high-latitudes from October by means of January.
The time interval concludes with January as a result of river customers have often shared open water places by then. River ice additionally turns into extra complicated later within the winter. Different SAR-based river ice classifications deal with spring ice throughout breakup.
“This may be personalized and automatic for any northern latitude rivers to offer present open water zone maps,” Engram mentioned. “It isn’t designed only for Alaska.”
Artificial aperture radar can penetrate clouds and different atmospheric circumstances akin to haze, fog and rain. It’s because SAR operates within the microwave portion of the electromagnetic spectrum, which has longer wavelengths than seen mild.
SAR know-how is broadly used for environmental monitoring, agriculture, catastrophe administration and protection.
Engram and the staff refined and validated their knowledge processing to scale back the classifications to 4: ice, open water, much less sure ice and fewer sure open water.
To do that, they labored with two kinds of radar knowledge: vertical-vertical and vertical-horizontal.
For vertical-vertical, the electromagnetic wave of each the transmitted and returned radar beam has peaks and valleys, much like the rise and fall of ocean waves.
For vertical-horizontal, the transmitted electromagnetic wave is just like the ocean waves, however the wave getting back from the focused object is oriented side-to-side, much like how a snake strikes.
That is vital as a result of the completely different mixtures can reveal completely different knowledge options.
Knowledge can also be influenced by the angle at which the radar beam itself is geared toward a goal. Totally different angles can present completely different views and, subsequently, completely different data.
Engram used knowledge from the European House Company’s Sentinel-1 satellite tv for pc. This knowledge is archived at UAF’s Alaska Satellite tv for pc Facility.
The researchers then in contrast the SAR knowledge with aerial pictures, the sphere of view of dozens of shore-based cameras, aerial pictures, on-ice observations and stories from group members who uploaded observations to the observer portal.
“We had shore-based cameras all around the state, and so they took an image of the river every single day,” Engram mentioned. “And we consulted with communities, asking ‘What’s vital to you?'”
Engram selected sections of eight rivers: the Colville, Noatak, Tanana, Yukon, Kantishna, Innoko, Copper and Kuskokwim, listed right here in descending order of latitude.
The staff chosen places with completely different river volumes, widths, channel varieties and glacial silt content material. Additionally they selected places in each tundra and boreal forest, in addition to with variations in close by permafrost circumstances.
“With this ice classification, we’re making an attempt to tell apart between ice and open holes within the ice,” Engram mentioned. “Numerous research have been carried out, particularly in Canada, various kinds of ice. We did not try this. We simply went ice versus open water.”
The analysis was funded by the Nationwide Science Basis’s Navigating the New Arctic and Arctic Observing Community by means of the UAF Recent Eyes on Ice program and by NASA’s ROSES Citizen Science for Earth Techniques Program by means of the Neighborhood Eyes on River Ice mission.
Engram praised the Alaska Satellite tv for pc Facility, which hosts the info.
“We’re actually lucky in that scientists have entry to that knowledge, not simply on the College of Alaska Fairbanks, however worldwide,” she mentioned. “The Alaska Satellite tv for pc Facility has made SAR knowledge rather more usable for any sort of scientist. You do not have to be a SAR specialist.”
