Shrinking Polar Circle - AIRS Temperature Anomaly Trends in the Arctic

With a 20 year record from the AIRS instrument, we are able to examine trends in atmospheric temperature in the data. The animation on the left shows the global monthly mean temperatures for each month of the AIRS mission at a pressure level of 931 mb from the Version 2 of the CLIMCAPS-Aqua L3 data product.

The graph on the right shows in white the anomaly in temperature in the Arctic region obtained by taking the difference in the average temperature for each month from 60N to 90N from the average temperature for that month in this region over the entire time period. The white line through the data is a linear fit and shows an upward trend in the anomaly.

We also show in this figure a blue line that represents the ‘zero-anomaly latitude’ trendline defined as the starting latitude that would be required to have a zero anomaly when integrating poleward to 90N. We see that the zero-anomaly latitude moves poleward, indicating that less of the lower latitudes can be integrated to give an equivalent temperature to the average for the mission.

Back to the figure on the left, the blue circles show the starting point and time dependence of the zero anomaly latitude trendline. The AIRS data shown here are indicating a shrinking of the polar circle, as seen on other data sets.

At the time of the production of this animation, the observed trends seen in the data have not been validated. We share them with the community at this time to inspire further investigation and validation.