Animated Images of Arctic Sea Ice Extent Decline

This post shows how to download and animate a series of Arctic Sea Ice Extent images using R and the animation package.

In my previous post, I showed how to download the daily arctic sea ice extent  data and generate an animation of the time series plots. In this post I show how to animate the monthly images provided by NOAA’s Nation Snow and Ice Data Center.

###### RClimate Script: NSIDC_Monthly_Sea_Ice_Extent_Images.R
## Download and process 1981 to 2012 Monthly Arctic SIE Images
## Sept. 5, 2012: http://chartsgraphs.wordpress.com; DK O'Day
##############################################################
  library(animation)
## Establish work dir to place downloaded images and gif file
  setwd(getwd())
  where <- getwd()

## Monthly NSIDC Extent Immage Link
# ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Aug/N_198108_extn.png
  part_1 <- "ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Aug/N_"
  part_3 <- "08_extn.png"

# Specify month number for animation
  m <- "08"

# Loop through years to create link and download images
  for (y in 1981:2012) {
     file_name <- paste(part_1, y, part_3, sep="")
     copy_name <- paste(where, "//asie",y,m,".png",sep="")
     download.file(file_name, copy_name, mode="wb")
     }

## copy last file c times to extend gif animation
    for (c in 1:2)
    {
     file_name <- paste("asie2012",c, ".png",sep="")
     file.copy(from= copy_name, to = file_name, overwrite=T)
    }

## Use animation package to generate gif file
  ani.options(convert=shQuote('C:\\Program Files (x86)\\ImageMagick-6.7.9-Q16\\convert.exe'))
  ani.options(outdir = getwd()) # direct gif output file to working dir
  ani.options(interval= 0.70)
  im.convert("asie*.png", "asie_image_animation.gif")

Here is a link to the R script file.

R Script to Build Animation of Arctic Sea Ice Extent – Update 9/3/12

In my previous post I showed an animation of Arctic Sea Ice Extent from the 1980′s through August, 2012 (link).  In this post, I show how to build this Arctic Sea ice Extent  animated chart.

Source Data

The Arctic Ice Sea Monitor (link)   updates their daily csv file with the latest satellite based arctic sea ice measurements.  Here is the daily csv file link.

R script

To develop my animation of the daily Arctic Sea Ice extent, I decided to produce a plot for each year that showed the current year in red and the previous years in grey.  I go this idea from Tamino at Open Mind.

Here is my R script: link.

Once I have the individual png files for each year, I use Photoshop Elements to generate my animation.

After getting Pierre’s comment about using the animation package, I gave it another try. The 2nd time,  I got it to work with ease.

I can now update the daily ASIE plot automatically without any Photoshop Elements involvement.

Thanks Pierre.

Visualizing the Arctic Sea Ice Extent Decline

Understanding what is happening to Arctic sea ice is critical to recognizing the serious consequences of global warming. So I want to help people visualize the 30+ year trend in Arctic sea ice extent.

The source data file is here:  
http://www.ijis.iarc.uaf.edu/seaice/extent/plot.csv

September 2011 Arctic Sea Ice Extent Forecast

In this post, I use a quadratic regression model to forecast the  September, 2011  Arctic Sea Ice Extent. The model was developed with  1980 – 2010 data. Links to the R script, source data and  how-to article on polynomial regression are provided.

Arctic Sea Ice Extent Forecast for September, 2011

First, here is my forecast: (Click image to enlarge)

Based on the 1980 – 2010 downward Arctic Sea Ice trend,  my forecast is that September, 2011 SIE will decline  0.36 below 2010 levels, to 4.54 million km^2, with a confidence band of +- 0.59.

How Did I Develop My Forecast?

I have written a number of posts on Arctic Sea Ice Extent (here, here, here). In this post, I used the NSDIC‘s monthly data file (link)  to construct a quadratic regression model of September sea ice extent for the 1980 – 2010 period. I then used this model to predict the September, 2011  Arctic Sea Ice Extent.

I have 2 main learning curve sources for this model:

• Tamino‘s post on Arctic Sea Ice decline provided the basic idea of using a quadratic model to fit Arctic SIE decline.

• John Quick’s tutorial on polynomial regression provided the how-to instructions I needed to implement Tamino’s approach in R.

RClimate Script and Links

Here is the link to my RClimate script.

Arctic Update

I have restarted updating my Arctic Update Page which went into hibernation in late September, 2010 after the Sea Ice minimum was reached. I continue to be concerned about the rapid Arctic Sea ice decline, I see it as one of many threads of evidence on the serious consequences of global warming.

1/16/11 Update

After a break, I have restarted daily updates to my Arctic Update page.  I will start slowly,with just 4 charts and limited discussion.  I will be adding additional charts and analysis as the year unfolds.

Arctic SIE Trend for Latest Month

December, 2010 showed the lowest SIE in the1979-2010 period.

Arctic Sea Ice Extent Trends: 1979-2010; Update 1

Now that the 2010 Arctic sea ice melt season is over, we can see how 2010 fits into the long-term trends Arctic  Sea Ice Extent. This post shows an R Climate chart that I have made to look at the annual  NSIDC Arctic Sea Ice Extent maximum, minimum and seasonal melt trends for the 32 year period, 1979 to 2010. Data and RClimate scripts are provided.
Update 1 (10/6/10) Added trend lines to plots based on suggestion from reader.

Here’s my RClimate script trend chart of 1979-2010  NSIDC Arctic Sea Ice Extent data.  I have plotted NSIDC’s maximum and minimum sea ice extent for each year and my calculated value for seasonal melt (maximum – minimum). (Click image to enlarge)

Comparing 2010 and 2007 Arctic Sea Ice Extent Trends

See my Arctic Update Page for daily updates on Arctic Sea Ice Extent

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: