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.
The Danish ship Venta Maersk, (Maersk Line, ice-class Baltic feeder vessel of 3,600 containers) is going to attempt to transit across the Kara Sea, the Laptev Sea and the East Siberian Sea.
Maersk said: "The trial passage will enable us to explore the operational feasibility of container shipping through the Northern Sea Route and to collect data."
There is generally a lot happening in Arctic sea ice news at this time of the year as we head to the annual summer minimum extent, and current sea ice extent is currently about 1.6 million km2 below the 1981-2010 mean.
Given that the trend of minimum ice extent has been relentlessly downwards since the start of the satellite record:
we could expect the Venta Maersk to have potentially an easy passage.
But that is rarely true in polar seas - even at the height of what will be the Arctic summer.
A look at the distribution of the current sea ice extent is interesting.
There is more sea ice in the East Siberian Sea than we could expect (~40% more than the 1989-93 mean), and a look at the latest "near real time" (end of April 2018) ice thickness data from CPOM show that the ice in this region was quite thick at the start of the summer melt season.
Interestingly if you look at the Cryosat sea ice thickness map north of Greenland you can see that at the end of the winter the sea ice thickness was already relatively low. (See the story in the Guardian: Arctic’s strongest sea ice breaks up for first time on record). The thickest sea ice is further to the west north of the Canadian Arctic Archipelago.