Hey! Welcome to TFP!!
Water doesn't sit on top of mesh covers. That water is at the level of the water in your pool. The cover has sagged into the pool. You won't be able to pump the water "off" the cover, more will replace it from the pool.
Did the water on top of the cover freeze? (I can't quite tell from picture) Can you break it into smaller pieces and use your brush on a pole to push it off? That might help remove the leaves and debris from the cover. You might then check the level of the water in the pool, throw in a sump pump and lower it a bit, so the cover is no longer sitting in the pool water. I already had to pump out my pool when we had a monsoon after closing...had to drain another 8" Ugh...my cover too was dipping into the water.
Finally, on the cover, it is 8 years old, not too old, but certainly with age and events like this one (has this happened before?), they do start to sag. The springs also will stretch. How compressed are the springs? The one directly in front in the picture, to the right of the concrete stair mount, looks like it is completely stretched out. They should be about 1/2 way between un-compressed and compressed when installed correctly. What do the springs in that area look like? A pic or two would help.
In summary
1) get the debris off the cover
2) drain the pool back down (the cover will rebound a bit without debris and when it is no longer sitting in water)
3) check the springs. If they are fully compressed, you might want to try replacing that spring set, and adjusting tension to get 1/2 compressed.
4) if you still get sag in the middle, it is just cover wear and tear.
Hope that helps!