Ice Lakes

Ice Fishing & Holiday Savings! Use Code ICE2020 on Flagged Products! New Winter Hours: Our Retail Stores are open Wednesday - Sunday. Call Center is open 7 days a week! Ice thickness measurements are generally taken near the beginning of the month from October to June. Readings taken near the end of the month are appied to the following month. To view historical readings please select the month/year below. The definition of lake ice in can vary from lake to lake. For the citizen observers reporting data, ice in occurs when the entire lake is frozen over for the first time and the ice cover remains through winter. Observers do not report ice thickness.

In recent decades, we've become aware of lots of water on Earth that's deep under ice. In some cases, we've watched this water nervously, as it's deep underneath ice sheets, where it could lubricate the sheets' slide into the sea. But we've also discovered lakes that have been trapped under ice near the poles, possibly for millions of years, raising the prospect that they could harbor ancient ecosystems.

If you’re going skating or ice fishing with a group, stay off ice that’s less than four inches thick. As a general rule, avoid ice that has cracks or ice near inlets or moving water. If you’re not familar with an area, be sure to talk to the locals because ice is rarely the same thickness all the way across a body of water and can change. Thin Ice Warning Issued In Hennepin CountyDue to warm weather, the Hennepin County Sheriff's Office is asking people to stay off the lakes and ponds over the weekend.

Now, researchers are applying some of the same techniques that we've used to find those under-ice lakes to data from Mars. And the results support an earlier claim that there are bodies of water trapped under the polar ice of the red planet.

Spotting liquids from orbit

Mars clearly has extensive water locked away in the form of ice, and some of it cycles through the atmosphere as orbital cycles make one pole or the other a bit warmer. But there's not going to be pure liquid water on Mars—the temperatures just aren't high enough for very long, and the atmospheric pressures are far too low to keep any liquid water from boiling off into the atmosphere.

Calculations suggest, however, that liquid water is possible on Mars—just not on the surface. With enough dissolved salts, a water-rich brine could remain liquid at the temperatures prevalent on Mars—even in the polar areas. And if it's trapped under the Martian surface, there might be enough pressure to keep it liquid despite the thin atmosphere. That surface could be Martian soil, and people are thinking about that possibility. But the surface could also be one of the ice sheets we've spotted on Mars.

That possibility helped motivate the design of the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) on the Mars Express orbiter. MARSIS is a radar device that uses wavelengths that water ice is transparent to. As a result, most of the photons that come back to the instrument are reflected by the interface between ice and something else: the atmosphere, the underlying bedrock, and potentially any interface between the ice and a liquid brine underneath it.

And that's what the original results, published in 2018, seemed to indicate. In an area called Ultimi Scopuli near Mars' south pole. The researchers saw a bright reflection, distinct from the one caused by the underlying bedrock, at some specific locations under the ice. And they interpreted this as indicating a boundary between ice and some liquid brines.

Now with more data

Two things have changed since those earlier results were done. One is that Mars Express has continued to pass over Mars' polar regions, generating even more data for analysis. The second is that studies of ice-covered lakes on Earth have also advanced, with new ones identified from orbit using similar data. So some of the team behind the original work decided it was time to revisit the ice sheets at Ultimi Scopuli.

The analysis involves looking at details of the photons reflected back to the MARSIS instrument from a 250 x 300 square kilometer area. One aspect of that is the basic reflectivity of the different layers that can be discerned from the data. Other aspects of the signal can tell us about how smooth the surface of the reflective boundaries are and whether the nature of the boundary changes suddenly.

For example, the transition from an ice-bedrock boundary to an ice-brine one would cause a sudden shift from a relatively weak, uneven signal to a brighter and smoother one.

The researchers generated separate maps of the intensity and the smoothness of the signal and found that the maps largely overlapped, giving them confidence that they were identifying real transitions in the surfaces. A separate measure of the material (called permittivity) showed that it was high in the same location.

Overall, the researchers found that the largest area that's likely to have water under the ice as about 20 by 30 kilometers. And it's separated by bedrock features from a number of similar but smaller bodies. Calling these bodies 'lakes' is speculative, given that we have no idea how deep they are. But the data certainly is consistent with some sort of under-ice feature—even if we use the standards of detection that have been used for under-ice lakes on Earth.

How did that get there?

The obvious question following the assumption that these bodies are filled with a watery brine is how that much liquid ended up there. We know that these salty solutions can stay liquid at temperatures far below the freezing point. But the conditions on Mars are such that most of minimum temperatures for water to remain liquid are right at the edge of the possible conditions at the site of the polar ice sheets. So some people have suggested geological activity as a possible source of heat to keep things liquid.

That's not necessarily as unlikely as it may sound. Some groups have proposed that some features indicate that there was magma on the surface of Mars as recently as 2 million years ago. But the researchers here argue that if things are on the edge of working under current climate conditions, there's no need to resort to anything exceptional.

Ice Lakes Trail

Instead, they suggest that the sorts of salts we already know are present on Mars can absorb water vapor out of the thin Martian atmosphere. Once formed, these can remain liquid down to 150 Kelvin, when the local temperatures at Ultimi Scopuli are likely to be in the area of 160 Kelvin and increase with depth.

And if that's true, there could be liquid in many more locations at Mars' poles. Not all of them are as amenable to orbital imaging as Ultimi Scopuli, but it's a safe bet that this team will try to find additional ones.

Ice Lakes Durango

Nature Astronomy, 2020. DOI: 10.1038/s41550-020-1200-6 (About DOIs).

Ice Lake Chipset

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  Friday, December 11, 2020 - 11:45 AM MST

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  Wednesday, December 2, 2020 - 1:09 PM MST

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• Here are the top reasons to go ice fishing this winter

  Monday, November 30, 2020 - 4:27 PM MST

  If you haven't tried ice fishing in Idaho yet, you're missing out on a winter activity that is not only fun and inexpensive, it's a great way to catch lots of tasty fish.

• Anglers will get new ice fishing access at Lake Cascade this winter

  Wednesday, November 25, 2020 - 9:40 AM MST

  Anglers looking for access to Lake Cascade for ice fishing will get a new option this winter with the addition of the Boulder Creek walk-in access and parking lot. Lake Cascade State Park staff developed the area so it can be plowed, and Fish and Game hired a contractor to keep it clear of snow during the ice fishing season.