This is just a brief post to note the arrival of widespread sea ice around and north of Point Barrow in the past few days. The NWS-Anchorage sea ice analysis from Friday showed a large gain in ice cover that connected the shore ice to the Arctic pack for the first time:
It's interesting to observe that cooler temperatures developed quickly at Barrow in the wake of the sea ice formation; the low was 4 °F yesterday, and a significant low-level temperature inversion was observed for the first time since September 16 (see yesterday's 3am and 3pm soundings below). Prior to sea ice formation, strong surface warming from the adjacent ocean waters tends to produce a steep low-level lapse rate (warm below, cold above) in the lowest levels of the atmosphere, but the heat source is reduced after most of the nearby ocean surface is frozen. These changes are evident in the climatological vertical temperature profile as discussed in an earlier post here.