Can Caliches Develop in Arctic Soils?

Caliche in the Arctic? Seriously?

Caliche, or calcrete as some call it, usually conjures up images of sun-baked landscapes. Think the American Southwest, the Australian Outback, maybe even the Kalahari Desert. These are the places where you expect to find this stuff – hardened layers of calcium carbonate that bind the soil together. But the Arctic? That’s a different story, right? Ice, snow, permafrost… not exactly caliche country. But hold on, because the answer to whether caliche can actually form up north is a surprising yes. It’s not the norm, but under the right circumstances, it absolutely can happen.

So, what exactly is caliche anyway? Basically, it’s calcium carbonate – the same stuff that makes up limestone and chalk – that’s precipitated out of water and glues soil particles together. Rainwater dissolves calcium carbonate in the topsoil and carries it down. Then, as the water evaporates, or as carbon dioxide levels change, that calcium carbonate comes out of solution and forms a hard layer. Warm temperatures help with the evaporation part, and plant roots add to the mix by releasing carbon dioxide.

Now, let’s talk about the Arctic. Arctic soils are a whole different ball game. We’re talking Cryosols here – soils defined by permafrost, that permanently frozen layer that’s like a concrete slab under the surface. This permafrost makes it tough for water to drain and really messes with how the soil develops. Plus, it’s cold! Biological activity grinds to a halt, weathering slows down to a crawl, and you end up with thin, not-so-developed soils that don’t have much organic material. And to top it off, the active layer – that bit of soil that thaws out in the summer – goes through constant freeze-thaw cycles, churning everything up like a washing machine.

So, with all that going on, how could caliche possibly form? Well, here’s the kicker: it all comes down to having the right ingredients. If the soil’s parent material – the stuff it’s made from – contains carbonate rocks, then you’ve got a shot. Think of glacial deposits or sediments that came from limestone bedrock. In those cases, calcium carbonate is already in the soil, just waiting for the right conditions.

I remember reading a study about East Greenland where researchers found calcrete crusts on glacial debris in areas with carbonate rocks underneath. What they figured out was that the permafrost was actually helping the process. Because the permafrost stops water from draining downwards, it creates a sort of “perched” water table. This forces dissolved minerals to either move sideways or get left behind on the surface as the water evaporates. Plus, the temperature difference between the top of the soil and the permafrost can cause limestone to dissolve near the permafrost and then precipitate out as calcium carbonate closer to the surface. Pretty neat, huh?

Even though the Arctic is generally cold and wet, some spots can be surprisingly dry due to low rainfall. These dry patches, combined with permafrost and carbonate-rich soil, can create the perfect storm for caliche formation.

Now, why does all this matter? Well, for one thing, it shows us just how complex soil development can be, even in the most extreme environments. It also means that we can’t automatically assume that caliche always means a dry climate. It can also form in permafrost areas under the right circumstances. And finally, as the permafrost thaws, it could change how much calcium is available in arctic soils, which could then affect carbon cycling and greenhouse gas emissions. Some studies even suggest that more calcium can actually reduce CO2 release from these soils.

Of course, we have to be careful when we’re looking at old caliche deposits to figure out what the climate was like in the past. The unique conditions in permafrost regions can lead to caliche formation that isn’t necessarily related to how dry the overall climate was.

So, there you have it. Caliche in the Arctic – it’s not a mirage! It’s a real thing that can happen when you’ve got the right combination of ingredients. Understanding how it forms in these unusual environments is key to understanding soil development, carbon cycling, and making accurate guesses about past climates. Who knew dirt could be so interesting?