Re-living the Last Glacial Maximum–well for a day, anyway

After yesterday’s re-acquaintance with winter, a brief period of snow falling here in Catalina for a few minutes, and a whopping 0.67 inches of rain, we have another deep winter day ahead.

Here’s the National Weather Service’s forecast for Catalina, at least elevations of about 3200 feet.

“Today: Snow showers likely before 2pm, then rain and snow showers likely. Partly sunny, with a high near 46. West southwest wind between 8 and 16 mph. Chance of precipitation is 60%. Total daytime snow accumulation of 2 to 4 inches possible.”

A glimpse of a Catalina paleoclimate

A day like this, with snow expected and daytime temperatures reaching only the mid-forties let’s us experience what Arizona was like in the springtime 15,000 years ago or so during the Last Glacial Maximum (sometimes called the Wisconsin Maximum, referring to the area around the Great Lakes where ice was really piled up–no wonder we get visitors from Wisconsin; they remember.)

But, let us not overlook the other areas of the country during that Last Glacial Maximum.  Ice was piled up more than a kilometer deep in Seattle!  I am not kidding.  Here is a shot of what the Space Needle might have looked like in those days of the Last Glacial Maximum when snow and ice were building up.  Its pretty impressive since the Space Needle is a few hundred feet high.  Hard to imagine, but there REALLY was ice deemed to have been 1 km deep in Seattle 15,000 years ago!

A huge amount of global warming took place, of course, after the Last Glacial Maximum, people started going back to Wisconsin and other northern climes.   The warm era that followed the end of the Last Glacial Maximum, and the one we are now in is called the “Holocene”, BTW.

However, our current era also has a rather dark moniker,  also being termed an “Interglacial” period, as were all those periods between ice ages in the Pleistocene when it was nice and comfy.  “Interglacial” sounds kind of temporary, and they were back then, only about 10, 000 to 20,000 years long, and we are about 12,000 years into the “Holocene.”  However the duration of interglacials is not pinned down real well and “orbital” forcing of ice ages (Milankovitch cycles, Wiki) puts the next one around 50,000 years from now.

Maybe it would be good to go look at some petroglyphs today and think about what the weather was like back then for those folks who made them.

Oops/Correction:  Actually, in researching “petroglyphs” they seem to have appeared AFTER the Last Glacial Maximum, about 7,000-9,000 years ago.   Hmmmph.  That petroglyphs would appear then is understandable.  People were happy it was warmer and took their happiness out on the rocks which were no longer so cold, thus explaining the world-wide burst of rock work.  I work hard to provide you with information like this, information you can’t get elsewhere.

Today’s clouds

Its so cold up top today!  Its -11 C at just around the top of Mt. Sara Lemmon.  Since the tops of the clouds over us, even shallow ones,  will be -15 c, and the deeper ones to -30 C today, lots of snow will form in them, and that means virga and rain/snow showers, graupel (soft hail likely).  The upper level trigger for most of this will begin affecting us this morning, and with a LITTLE heating, cumuliform clouds should begin enhancing the Stratocumulus deck we now have.

Lower clouds with lots of ice in them look like yesterday afternoon’s clouds, shown in the photo below.  That smooth texture on the left side of the photo is due to ice falling out, but the snowflakes and ice crystals are too small to reach the ground, except only the very largest.  The shaft in the distance is due to a much deeper cloud in which the snowflakes and graupel (soft hail) were able to grow far larger than in the other cloud regions nearby. That’s because it had much higher cloud top, forced by stronger updrafts.  The stronger the shafts, the the higher  topabove it is a pretty good rule.

Gee, starting to “graupel” right now at 6:31 AM AST!  Exciting.

So, look for a lot of smooth looking clouds today like those in this photo.