With the brightness temperature data set, brighter colours indicate higher temperatures. The Larsen Ice shelf and A68a are glacial ice and so cold, they appear dark purple. The sea ice is thinner and warmer and in contact with the ocean so the purple shade is lighter. The leads which are cracks in the sea ice and so open water and / or very thin sea ice appear as relatively bright lines. On the bottom right of that image you can see that under certain circumstances the brightness temperature data set can see through clouds.
As daylight has returned to Antarctica it is straightforward to pick out polynya forming on the edge of the Antarctic continent.
This one by the Stange Ice Shelf and Rydberg Peninsula caught my eye. It is a latent heat polynya formed as the winds push the sea ice away from the land to reveal the ocean that appears black beneath.
The wispy trails of grey which appear in the black are new sea ice forming as frazil ice.
This is the location of the peninsula.
I visited that area in 2007 and took this picture. You can a thin skim of young nilas ice in front of the ice shelf, and sea smoke too.
The Weddell Sea polynya is an area of open water that sometimes appears in the Weddell Sea over a relatively shallow region called Maud Rise.
In the latest satellite imagery from the DMSP satellite you can see the lower concentration sea ice as the darker blue colour. If you look at the MODIS imagery for the same date you can clear see black which indicates open water in the pack ice.
Trying to understand the geographic nature of the very low Antarctic sea ice extent I made the following animation:
The highlight issues in the graphic are the clear lack of sea ice in the Amundsen/Ross Seas and the Southern Ocean off Dronning Maud land. (If you are not familiar with the names off the seas / locations see the map below).
The Weddell Sea is has a relatively compressed sea ice cover this year - but it's clear there is large inter-annual variability.
Off Wilkes Land the sea ice is heavier this year - and it's easy for this to get lost in the headline story around the very low extent. There are several Antarctic research stations along this coast:
I was asked “what is an easy way to get a satellite image into Google Earth?”. Once I explained how I do it I thought it may be of interest to others. NASA have provided a really excellent web interface to some of their visual data called Worldview.
The Worldview description puts into perspective how good it is.
The Worldview tool from NASA's EOSDIS provides the capability to interactively browse global, full-resolution satellite imagery and then download the underlying data. Most of the 200+ available products are updated within three hours of observation, essentially showing the entire Earth as it looks "right now"
More than 200 data products within three hours…
Open worldview and this is the screen you are greeted with. It is easy to use. The key regions are the projection / copy / link tool in the yellow square on the right, the date control in the yellow box on the bottom of the browser screen and the layers control in the yellow box on the left.
I do recommend following the tour to find your way around the data sets.
If you click the layers button (red on the left) this is just a part of the choice of real time data you can easily access.
So you select the data you want to see, and then you can zoom in and easily download areas of interest. For some reason I always seem to find my way at this view
This movie I made shows how you can get imagery from Worldview easily into Google Earth.
I hope you find this useful. It's easy to spend a lot of time looking at this data.
The plot shows the difference between the daily ice extent, in each grid cell, for the year to 21 November 2016, and the mean, for each day, based on historical data for the 5 year period 1989-93.
Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean.
To make the plot for each day of the year and each grid cell I worked out the mean sea ice extent for 5-year period 1989-1993. I then used this calculated mean taken away from the 2016 data for the same day to derive the anomaly maps.
For example if the plot shows very dark blue that means that there is 100% sea ice cover in that grid cell in 2016 and none in the 1989-93 mean. A dark red means there is no sea ice in 2016 where we would expect 100% sea ice cover.
The original data come from the DMSP SMMI data set at the NSIDC.
The seasonal cycle of sea ice extent in Antarctica has been fairly stable over the length of the satellite record. There is a slow growth of sea ice from a minimum of ~3x106 km2 in February to a maximum of ~19 x106km2 in September, before there is a relatively rapid fall in the Antarctic spring.
But this year something different is happening.
Below is Tamino's image for the Southern Hemisphere sea ice extent, the red line is 2016 up to 16 November 2016.
From January up to September the sea ice extent in 2016 follows all previous data.
You can see that the polynya in the centre of the picture can be seen from the very beginning. This is forming in front of the Dotson Ice Shelf - and from the scale bar you can see it is big. This polynya really starts to develop as open water around 5 October 2016.
The coastal polynya on the northern land boundary appear in mid September - and develop throughout the record.
The image below was in my previous post and it shows the three polynya from a MODIS image on 9 October 2016.
Next diversion will be a area of open water / time plot.
The Amundsen Sea currently has some very large polynya. In front of the Dotson, Getz and Pine Island ice shelves they are clear in the satellite data.
A polynya is an area of open water in the winter pack ice.
These are likely latent heat polynya, and strong winds are pushing the sea ice away from the coasts to make the open water. In the open water there will be a lot of sea ice generation. I wouldn't be surprised if the weather that is keeping the sea ice compressed against the Antarctic Peninsula is also responsible for opening them.
Taking the MODIS data from the TERRA satellite and importing that into google earth, the open water shows up as black. At the top of the image in front of Pine Island Glacier the polynya are partially obscured by cloud.
In Google Earth you can measure the area quite easily.