Temperatures over land vs over water

By Rick Thoman
Alaska Climate Specialist
Alaska Center for Climate Assessment and Preparedness
International Arctic Research Center/University of Alaska Fairbanks

June temperatures on land averaged just a bit below the long-term average across most of the region. However, ocean temperatures were generally above the long-term normal. From 1985 to 2013, the average sea surface temperature offshore of Nome for June was about 40°F. Since then, it's been about 45°F. That does not sound like a big increase, but last month, the average temperature of 43.7°F, which was more than one degrees above the 1991-2020 average even though it was a bit below the post-2013 average.
In fact, this June, the average water temperatures offshore of Nome were higher than the June average of every year prior to 2014 except for 2005. Why were water temperatures warmer than the long-term average? A big factor was likely the many sunny days in June. At this time of year, with the long days and sun high in the sky, the dark ocean waters “soak up” the warming from the sun.
Another factor was likely timing of the loss of sea ice. While the shorefast ice in front of town did not break away until the evening of May 20, there was open water beyond the fast ice through much of May, again exposing the water to the heating power of the sunshine. Of course, water in the ocean is not like water in a lake. Ocean water is constantly in motion from the tides and currents. So when we say the ocean was warmer than average in June, what we really mean is that the water passing by Nome was warm.