In this post I present a chart that tracks the daily Arctic Sea ice Extent (SIE) for 2007 and 2010. I chose 2007 as the comparison year because it had the record minimum and I wanted to be able to directly compare 2010 with the record minimum year to get a quick comparison of 2010 with the minimum year.
I will update this chart regularly on my Arctic Update page to help Arctic Sea Ice observers get a quick sense of the 2010 – 2007 comparison.
2010 – 2007 Comparison Chart
Here’s my R based 2010 – 2007 Arctic SIE extent chart. (Click image to enlarge)
I’ve added a number of features to this chart to help me quickly asses the situation:
- Date of last JAXA data update noted in chart title
- Shows only 2007 (blue) and 2010 (red) data series to simplify comparison
- x axis Shows calendar year to date
- y axis scaled to range of values in period
- Comparison note on delta between 2010 and 2007 (top left)
- Maximum SIEs for both 2007 and 2010 shown with filled circle and values in legend
- Last reading SIEs for 2010 and 207 shown as filled stars and values in legend
- Calculated SIE Decline rates for previous 2, 5, 7,10,20,30,60 and 90 days shown in table provide direct comparison of trend rates between years.
My observations on 2010 versus 2007 Arctic SIE Trends So Far
As I viewed the JAXA daily chart each day, I found that I wanted specific information displayed on the chart so that I could see how 2010 was evolving. Here’s what I have observed so far:
- 2010 maximum SIE occurred 3 weeks later and 0.46 million k^2 more than the 2007 SIE.
- 2010 April – June decline rate has been much steeper than the 2007 rates. Using the 2010/2007 decline rate ratio:
- Previous 90 days: 1.51
- Previous 30 days: 1.29
- Previous 7 days: 1.14
- Previous 3 days: 1.05
- Previous 2 days: 1.22
- Watching the decline rate ratio gives me a quick indication of changes in the 2010 and 2007 decline rate ratios.
- As of 6/27, 2010 is -0.602 million km^2 less than the 2007 SIE. This indicates that 2010 could well be a record minimum year., depending on what happens in the next 70 – 80 days.
- If the 2010/2007 decline rate stays above 1, 2010 will be a record-setting year.
- While the 2010/2007 decline ratio can drop below 1 for a few days because of the 2010 – 2007 delta of -0.602 million km^2, this delta could be whipped out in short order if the 2010/2007 ratio drops below 1 for an extended period.
To make this chart, I’ve learned several new R techniques, including adding a table to a plot and sing a function in a for loop to generate the decline rates table.
My R script is available at this link.
The JAXA source data csv file is available at this link.