Not having ridden more than a few miles each day in over a year, I wanted to start exercising again with a short-medium ride (~15km/~9.5 miles). I did so over the course of an hour this morning. The area I ride in is known for its hills (I'm not sure what the grades/elevation changes are, but some of them are very tough.)
I ate a few bites of a Cliff Bar along the way and drank about 12oz of the 24oz of ice water I carried.
When I returned and began stretching before I showered, I noticed that the skin around my belly/abdomen was much cooler than the rest of my body.
[The following are my guesses at the answer to the question, none of which I'm entirely satisfied with. A good answer will not only address the title question but also address these thoughts.]
At first I thought this was simply the result of the body diverting blood from my stomach to my legs, in order to keep them oxygenated as I climbed.
However, I also know that the body needs to circulate blood between around the stomach to transfer excess heat to the ice water I drink; equivalently, the blood needs to reach the stomach to be cooled off so that, in circulating, it cools the rest of my body. Why then was my stomach not warm?
Then I considered that perhaps the body was diverting some resources to keeping the stomach cool in order to allow it to continue to process and absorb the ice water: intuitively, this makes some sense. Warm water on a ride seldom gets absorbed by the stomach, or so I've been told.
I suppose the coolness could simply be the result of the ice water—but this indicates that either the cold was not being spread to the rest of my body, or that it was maintained as a sort of "ice pack" at my core.