Monthly Archives: August 2018

52 Comments

Just over a year ago in July 2017 iceberg A68 calved from the Larsen C Ice Shelf. I appeared on BBC News before it actually calved explaining what was happening.

At first A68 was slow to move and as I predicted back then, it likely got stuck on the sea bed (we say "grounded"). It has stayed pretty much in the same place through to July 2018.

But now A68 has started to swing northwards.

As the light is coming back to Antarctica, at high latitudes visual imagery is very washed out. But if we look at other data such as the brightness temperature, you can see some striking features.

This image is from 20 August 2018.

Corrected Reflectance (True Color) from the Suomi NPP Visible Infrared Imaging Radiometer Suite (VIIRS), and the Brightness Temperature (Band I5, Day).
Corrected Reflectance (True Color) from the Suomi NPP Visible Infrared Imaging Radiometer Suite (VIIRS), and the Brightness Temperature (Band I5, Day). Image from 20 August 2018.

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.

...continue reading

13 Comments

A story on the BBC Business News website about the Northern Sea Route caught my eye:

Screen Grab of the BBC News WWW site story.
BBC Business News "Container ship to break the ice on Russian Arctic route". 21 August 2018.

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.

Sea ice in the Arctic currently about 1.6 million km2 below the 1981-2010 mean. 21 August 2018.
Sea ice in the Arctic currently about 1.6 million km2 below the 1981-2010 mean. 21 August 2018.

Given that the trend of minimum ice extent has been relentlessly downwards since the start of the satellite record:

Annual Arctic minimum sea ice extent. Data from from NSDIC.
Annual Arctic minimum sea ice extent. Data from from NSDIC.

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.

Arctic sea ice 21 August 2018, mean Arctic sea ice 21 August 1989-93 and difference between the two. Reds indicate absence of sea ice compared to the older data and blues indicate increased. The yellow box indicates a region where there is much more sea ice than we could expect.
Arctic sea ice 21 August 2018, mean Arctic sea ice 21 August 1989-93 and difference between the two. Reds indicate absence of sea ice compared to the older data and blues indicate increased. The yellow box indicates a region where there is much more sea ice than we could expect.

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.

Arctic sea ice thickness processed at UCL from CryoSat's SAR mode data: NOTE THIS IS END OF APRIL 2018. NRT Service Suspended during Arctic summer (May-Sept).
Arctic sea ice thickness processed at UCL from CryoSat's SAR mode data: NOTE THIS IS END OF APRIL 2018. NRT Service Suspended during Arctic summer (May-Sept).

It is possible the Venta Maersk could find the going slow, but she is a polar rated ship designed to work in the Baltic, and by staying close to the coast she could avoid the ice completely.

It is an interesting way to move a Baltic ship from it's build location in China to its planned operational area, and one to watch over the next month.

The excellent researcher Dr Nathanael Melia wrote a great post about the potential of Arctic Shipping on Carbon Brief in 2016: What will sea ice loss mean for Arctic shipping?

**

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.

Arctic sea ice thickness processed at UCL from CryoSat's SAR mode data: NOTE THIS IS END OF APRIL 2018. NRT Service Suspended during Arctic summer (May-Sept).
Arctic sea ice thickness processed at UCL from CryoSat's SAR mode data: NOTE THIS IS END OF APRIL 2018. NRT Service Suspended during Arctic summer (May-Sept).

***  UPDATE From Twitter

From Dr Stefan Hendricks at the Alfred Wegener Institute

Tweet from Dr Stefan Hendricks.
Tweet from Dr Stefan Hendricks.

**** Update 2 from Twitter

From Dr Ruth Mottram at the Danish Meteorological Institute.

Tweet from Dr Ruth Mottram
Tweet from Dr Ruth Mottram.