From Climate Warehouse
Mark Morano
https://arcfieldweather.com/blog/2024/7/30/715-am-another-summer-with-nearly-normal-temperature-in-the-arctic-region-continues-a-long-term-trend- in melting season
Meteorologist Paul Dorrian
Overview
We’re halfway through summer in the Arctic, and overall temperatures this season are repeating a pattern that started years ago, with near-normal levels that happen to be very close to freezing. The Arctic cold season is characterized by above-normal temperatures across the Arctic, a pattern that has been remarkably consistent in recent years. However, in terms of Arctic sea ice extent, summer temperatures in June, July and August are most important because this is the melt season in this part of the world. As long as summer (melt) season temperatures remain near normal, the potential for further significant sea ice reductions will be limited. In fact, given ongoing summer temperature trends in recent years, Arctic sea ice has shown resilience in both extent and volume. One possible explanation for this persistent temperature pattern, with near-normal summer conditions in the Arctic and above-normal temperatures during the other nine months of the year, the cold season, is an increase in the amount of water vapor in the atmosphere.
Arctic temperatures and their impact on sea ice
In fact, temperatures in the Arctic have been showing a consistent trend over the past few years, dating back to the early 21st century. Specifically, temperatures remain close to normal during the all-important summer (melt) season (June, July, and August), and then are typically much higher during the remaining nine months of the year at normal levels.
Summer temperatures in June, July and August are near normal, often near or slightly above freezing, and as long as temperatures remain at that level during the melt (summer) season, the potential for significant Arctic sea ice losses will be limited. Well-above-normal temperatures during the other nine months of the year have little impact on Arctic sea ice melt because they are typically well below freezing. In fact, thanks to this reliable temperature trend in recent years, Arctic sea ice has been quite resilient in both extent and volume.
Arctic sea ice extent has been below normal since the mid-1990s, when a major shift in the Atlantic Decadal Oscillation (AMO) resulted in above-normal North Atlantic sea surface temperatures. After that shift, Arctic sea ice extent steadily declined, reaching its lowest point in 2012, reaching levels not seen in the satellite era since the late 1970s. Since then, Arctic sea ice extent has remained fairly stable over the past decade or so, with an overall sideways trend.
except sea ice degreean important climate indicator to monitor is sea ice volume Because it depends on the thickness and extent of the ice. Arctic sea ice volume is difficult to continuously monitor because observations from satellites, submarines, and in-situ measurements are subject to space and time constraints. Therefore, one of the best ways to estimate sea ice volume is to use numerical models that exploit all available observations. One such computer model comes from the University of Washington and is called the Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS, Zhang and Rothrock, 2003). Arctic sea ice volumes derived from the model show a steady downward trend from the mid-1990s to a low reached in 2012.
Possible effects of water vapor
One possible explanation for the temperature changes in the Arctic over the past few decades has to do with the increase in the amount of water vapor in the atmosphere. Overall, the Arctic has experienced higher than normal water vapor levels over the past few decades, primarily due to the North Atlantic (positive AMO) and Pacific Ocean (multiple El Niño events).
Because the water is warmer than normal, evaporation increases, creating more water vapor in the atmosphere. In very cold and dry atmospheres, increased water vapor will have a greater effect on temperature, while in warmer and wetter environments it will have a smaller effect. In other words, an increase in overall water vapor is likely to lead to above-normal temperatures during the cold season in the Arctic, which is typically very cold and dry, while during the warm season the effect is likely to be minimal, if any ).
Meteorologist Paul Dorrian
Uckfield
arcfieldweather.com
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