I'm back !
I'm looking the current GFS 10 day MAX 2M temp forecast. It's nicely color coded for low IQ folks like me.
In the center of the map, very close to 90N is a big chunk of real estate that's forecast to hit 3C.
It's surrounded by area that is only forecast to reach 2C.
Some of the very smart people on the melting season thread are telling me that the presence of ice limits the temperature to near freezing. If that's the case, how is the North Pole hitting 3C?
Other smart people say there is an exception for warm air advection from land. But there isn't any land near 90N.
Which factors determine the 2M temperature at 90N?
Ok, here my take as a total amateur:
To begin with, let's think about why meteorologists use 2M temparatures, and not surface temparatures. The simple answer is: 2M temparatures are more correct when it comes to weather because they are not as influenced by the state of the surface.
If there is ice, then the air temperature at the surface will always tend to 0 degres C. In still air, it is very possible to have several degrees higher temparatures at 2M, with the colder surface air staying at the surface, with very little heat transfer downwards.
But if there is any wind then the air keeps getting mixed up, with warmer air hitting the ground and colder air being swept up. If the air being blown in by the wind is warm enough, then you might still see the same temperature profile as in very still air, with near 0 at the surface and 2 -3 at 2M.
You have to remember that wind does not only flow along the ground, but very often is flowing down or up depending on weather systems such as fronts, highs and lows. So a warm downwelling wind with turbulence at the surface could quite happily maintain a profile of 0 degrees at the ice surface, 2 or 3 at 2 meters and higher temps at higher altitudes.
So looking at temperatures only tells you a very limited part of what is actually happening. Is the air moving, how is it moving, what is the temperature of the air being brought into the system along the surface and / or from higher up?
And then you have to look at humidity and dew point as well if you want to get a grasp of whether the ice is melting or not. If relatively warm and humid air is being transported in over the Arctic and flushed downward, then the water vapor will condense on the ice, releasing significant amounts of energy that goes into melting the ice - without changing the average temperatures at all!
Take a look at the Arctic in Nullschool today. You will see winds "starting" over Beaufort and "ending" over Laptev. This is because over the Beaufort, air is sinking, while over the Laptev the air is rising. If the air that is sinking over the Beaufort is warm and moist, then a hell of a lot of melt can happen there, even with a temperature of only 2 or 3 at 2M.