Alkaline battery performance at -30 Celsius
Each manufacturer of a battery chemistry category will try and evaluate the temperature behavior of their commercial technologies, because doing so may give them a new market worth pursuing. (Or let them know which markets NOT to pursue.) Some battery types don't even work until the temperature is over \$60^\circ\text{C}\$. While that might seem bad, it's good too as in some hot areas in the world this means the battery is preserved well until the temperature is driven up a little. (They have nice "shelf lives" in hot climates.)

Probably the best researched and most often recommended battery technology for low temperatures in the \$-30^\circ\text{C}\$ area is NiCd chemistry. These types have been well-characterized down to operation at \$-40^\circ\text{C}\$ and documentation on using them in cold temperatures dates back many decades. So lots of experience using them in cold situations to inform your decision.

Since their electrolyte isn't diluted during discharge, the freezing temperature remains at about \$-83^\circ\text{C}\$ regardless of discharge state. And NiCd batteries can still deliver perhaps a quarter to a third of their rated capacity (I've seen charts showing as much as 40%) when operating at \$-40^\circ\text{C}\$. Remarkably, too, they can also accept a charge at these low temperatures and aren't damaged by over-charging (or under-charging.) (However, over-charging still may generate some gas and water loss.) They aren't damaged, if they do freeze (go below \$-83^\circ\text{C}\$.)

Of course, they are in a different category from alkaline. (Primary vs secondary.) So it still may not be applicable in your case. But since you mention only occasional current pulses (which NiCd can handle well) and mention a reasonable period of operation, I think you may still find that some readily available version of NiCd will satisfy your needs. I'd start there. See where it takes you.

There is a publication called "Cold Regions Technical Digest" where they cover some of these details. There are other sources I have used, as well, to write the above text.