Alaska scientists use satellite to detect open water on otherwise frozen rivers

A photograph of nan Tanana River from Salcha contributed to Fresh Eyes connected Ice. (Tori Brannan)

Scientists astatine nan University of Alaska Fairbanks person developed a measurement to usage satellites to observe unfastened h2o connected different stiff rivers.

Open h2o tin beryllium vulnerable for Alaskans who dangle connected stream crystal to get around, and having reliable accusation astir specified hazards could make it safer for those walking connected nan ice.

Enter Synthetic Aperture Radar. That’s erstwhile a outer bounces a radar beam disconnected nan Earth’s aboveground and measures what comes back. UAF researchers figured retired really to look astatine that information and categorize nan crystal conditions connected each sorts of different Alaska rivers from astir October to January.

Remote Sensing Specialist Melanie Engram pinch nan Water and Environmental Research Center astatine UAF was lead writer connected nan study, published successful March successful nan diary Remote Sensing of nan Environment. Engram says Synthetic Aperture Radar, aliases SAR, is simply a awesome instrumentality for Alaska, because it doesn’t dangle connected daylight and tin penetrate unreality cover.

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This question and reply has been lightly edited for magnitude and clarity.

Melanie Engram: We person long, acheronian winters wherever optical imagery is uncommon aliases or not disposable astatine all. So having an progressive instrument, specified arsenic SAR, that tin supply its ain illumination is really useful successful particularly successful bluish world subject studies.

Casey Grove: Does it overgarment a picture? Does it show you nan extent aliases nan value of nan ice? How does it work?

ME: We looked astatine a mini area of nan stream that we had. We besides took a photograph that was pointed down connected nan crystal pinch shore-based cameras to train nan classification. So we could we could see, “Oh, that’s unfastened h2o successful nan photo.” And then, “What do we person successful SAR?” And past we would see, “Oh, there’s crystal and crystal cover. It’s unsmooth crystal covered aliases soft crystal covered.” So it was beautiful much, “Let’s look and see.” Look and spot what is, erstwhile nan stream is open, this is what nan SAR values are. When nan stream has crystal connected it, this is what nan SAR values are. We utilized shore-based cameras. We utilized national subject photos that were uploaded to nan Fresh Eyes connected Ice photograph portal. And past we besides went retired connected nan crystal successful January of 2021, connected a agelong of nan Tanana River adjacent present to Fairbanks.

CG: Yeah, for nan fieldwork that you really had to spell do, it wasn’t for illustration you were conscionable sitting successful an agency and looking astatine what nan outer told you, right? You really had to spell retired successful immoderate reasonably acold temperatures, right?

ME: Yeah, it was. It was much than 20 below, 26 beneath was nan coldest, I think. We went retired connected snowmachine. You could spot the, you know, nan steam coming up from nan from unfastened water. So location were unfastened h2o zones, moreover successful precocious January. That was adjuvant for us. We went down arsenic acold arsenic we could until location was unfastened h2o toward Nenana that we couldn’t we couldn’t spell immoderate farther.

CG: I mean, that’s benignant of nan point, right? To thief group understand what nan stream is doing, you know, who whitethorn beryllium retired location walking by snowmachine? Did it benignant of thrust location that constituent for you and benignant of return it retired of nan theoretical realm into nan existent world wherever you were really for illustration seeing nan unfastened water?

ME: Yes. And that’s why they they brought maine along. So I’m a elder citizen, but I thought it was really important to get retired location and spot it myself and say, “Well, oh, OK, this is this is what nan stream crystal is like. These are immoderate different things we mightiness want to consider.” We pulled up large blocks of ice, and we looked to spot if it was clear crystal aliases if location was sediment that was stiff successful nan ice, and I ne'er would person thought of that sitting successful nan office. So I deliberation it’s really important to get retired location and really put your boots connected nan crushed of what you’re studying