"Surface air pressure" refers to the force exerted by air molecules on the Earth's surface. It tells us how much air is pushing down on a certain area. Full definition
As for accelerated warming in the Arctic, that takes increasingly negative NAO / AO episodes to do that, while all the GCM's predict increasingly lower near surface air pressure in the Arctic, implying more positive NAO / AO conditions. (judithcurry.com)
The AO is a measurement of surface air pressure at the high latitudes over and north of Greenland. (washingtonpost.com)
The figure shows how surface air pressure changed throughout Martian history. (sciencedaily.com)