Tag Archives: sea ice

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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

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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.

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I love watching the opening of a polynya in satellite data. This is North Water at the NW tip of Greenland expanding over 6 days.  You can see the wind is to the SW and it is both pushing the mobile sea ice away from the fast ice of Nares Strait (the strait is named for George Nares), and the growth of new sea ice.

The Opening of North Water 9-14 May 2018.
The Opening of North Water 9-14 May 2018.

This is the location of North Water. It is a famous polynya and important for the local wildlife and first peoples.

The location of the polynya region.
The location of the polynya region.

The image below from the 14 May 2018 shows streaks of frazil ice. So what you can see is as well as the wind pushing the sea ice away from the fast ice, new sea ice is being generated.

North Water on the 14 May 2018 showing frazil ice streaks.
North Water on the 14 May 2018 showing frazil ice streaks.

One to watch in the next week.

Iceberg A68 calved from the Larsen C ice shelf earlier this year. I wrote about before.

As the berg calved it is starting to reveal a patch of seafloor that has been covered by thick glacial ice, and as the BAS press release says this has revealed:

a mysterious marine ecosystem that’s been hidden beneath an Antarctic ice shelf for up to 120,000 years.

To have the chance of making  observations in an untouched environment like that is so exciting, that the British Antarctic Survey are running an expedition to investigate. You can read about it in a great piece by Victoria Gill on the BBC news site, and the brilliant Katrin Linse has done some great work with Radio 4 and the BBC Breakfast program (2hrs 20 mins in source BAS twitter account) explaining both the purpose and the work.

I was looking this morning at the recent Sentinel-1 imagery on Polarview, this is an image of A68 captured on 11 February 2018. It's big - about 5,200 km2.

Iceberg A68 and the Larsen C Ice shelf captured from with the Sentinel-1 SAR sensor 11 February 2018.
Iceberg A68 and the Larsen C Ice shelf captured from with the Sentinel-1 SAR sensor 11 February 2018.

I labelled some features in the image: the iceberg and the ice shelf are the relatively solid grey colour. The blue overlay is where land and the ice shelf roughly were (it's called a land mask).

One thing you can see is the speckled grey colour which covers the top right hand side.

This speckled grey is sea ice.

It's a relatively thin cover of a typically 1-3 m thick.

Antarctic Sea ice.
Antarctic Sea ice.

If you map the current sea ice distribution, and the location of iceberg A68 you can see how much sea ice they are going to have to sail through to reach the region.

Larsen C, the iceberg A68 and the sea ice extent on 11 February 2018.
Larsen C, the iceberg A68 and the sea ice extent on 11 February 2018.

There is a lot of high concentration sea ice between the ice edge and the iceberg that the ship will have to traverse. RRS James Clark Ross is a very capable ship, and she will be able to make way through the ice.

The issue is this can take a lot of time.

And time whilst ice breaking is fuel.

In open water a research ship can cover ~22 km per hour, in sea ice if you are breaking ice then maybe 5 km per hour would be good, and you probably wouldn't break ice 24 hours per day.

They have 3 weeks.

Plus if you sail 400 km in the ice, unfavourable winds can easily compress the sea ice and trap a ship. It's happened before, and in the modern era even capable ships get can get held up.

The satellite I used to make the image doesn't do so well in coastal regions, so given some favourable winds there could be a nice channel for them. I am going to be watching the visible satellite imagery for that.

It's easy to make pronouncements from 14,000 km away, but really the people on the ground will  work it out.

Whatever happens I know that the researchers on board will do some great research. Plus I would be surprised if A68 moves too far from the region in the next year.

Breaking ice in Antarctica.

Breaking Antarctic sea ice on the RRS James Clark Ross.
Breaking Antarctic sea ice on the RRS James Clark Ross.

(Apologies to the Rolling Stones  for the title,

But if you try sometimes, you might find you get what you need.

*** Update 16 Feb 2028

This on twitter from Dr Stef Lhermitte

At the moment they will have to get through ~300 km of sea ice.

Being interested in the Weddell Polynya I plotted some time series data from 1 September 2017 to 23 November 2017. On the left-hand panel, you can see the see the sea ice concentration, on the right-hand panel, the anomaly of the concentration each day compared with a mean from 1989-93.

The Weddell Polynya is the low concentration region at approximately 12:00 in the movies below.

 

You can see the Weddell Polynya isn’t stationary.

You can also see the sea ice is still relatively low compared to the historic record. We should expect this after the extreme low sea ice from ~October 2016 onward.

Antarctic sea ice extent (with greater >15% sea ice cover) 23 November 2017. From NSIDC.
Antarctic sea ice extent (with greater >15% sea ice cover) 23 November 2017. From NSIDC.

I will write some more about this next week but for interest here is the Antarctic sea ice extent anomaly for 2017.

I made these movies using the excellent Antarctic Mapping Toolbox by Chad Greene. Antarctica is the Landsat Image Mosaic Of Antarctica (LIMA), and the coastline and shelf outlines come from the BEDMAP2 data set. Sea ice data is from NSDIC.

Antarctic sea ice extent remains low compared with the 1981-2010 median extent. This image shows the mean from 1989-93, the extent on 20 November 2017 and the difference between the two. Red colours imply that there is a decreased sea ice extent compared with the mean.

The mean Antarctic sea ice for the years 1989-93 on 20 Nov, the sea ice concentration on 20 Nov 2017 and the difference between the two data sets. Reds imply decreased sea ice compared with the mean, blue shades imply more. The original data come from the DMSP SMMI data set at the NSIDC.
The mean Antarctic sea ice for the years 1989-93 on 20 Nov, the sea ice concentration on 20 Nov 2017 and the difference between the two data sets. Reds imply decreased sea ice compared with the mean, blue shades imply more. The original data come from the DMSP SMMI data set at the NSIDC.

And obvious low region is the vicinity of the Weddell Sea Polynya. I have written about the polynya this season on 17 September and 25 September, as well showing how it developed through the winter on 11 September 2017.

Something exciting is happening in the ocean under the polynya, and based on new data sources such as the SOCCOM buoy that surfaced in the polynya:

Last month, SOCCOM scientists were astonished to discover that a float in the Weddell Sea had surfaced inside the polynya, making contact with satellites in the dead of winter. Its new ocean measurements, transmitted when it surfaced, are being analyzed as part of a study in preparation on Weddell Sea polynyas. With these new observations comes the possibility that the polynya’s secrets may finally be revealed.

We should expect some exciting research articles soon.

Sea ice extent currently ~1.2 million km2 low

The overall sea ice extent is currently ~1.2 million km2 below 1981-2010 median extent. This sounds a lot.

Antarctic sea ice extent (with greater >15% sea ice cover) 18 November 2017. From NSIDC.
Antarctic sea ice extent (with greater >15% sea ice cover) 18 November 2017. From NSIDC.

But at this time of the year the Antarctic sea ice is about to dramatically fall as spring develops. If spring "arrives" early then the extent will - as we see, be relatively low.

Seasonal cycle of Antarctic sea ice extent
Seasonal cycle of Antarctic sea ice extent

Whilst the full on development and opening of the Weddell / Maud Rise Polynya is unusual, if you compare the sea ice on 18 November 2017 with the extent from the same day on 1989-1995 it is clear that the extent is often lower over Maud Rise, at this time.

This is the sea ice on 18 November for 1989, 91, 92, 93, 94, 95 and 18 November 2017. The original data come from the DMSP SMMI data set at the NSIDC.
This is the sea ice on 18 November for 1989, 91, 92, 93, 94, 95 and 18 November 2017. The original data come from the DMSP SMMI data set at the NSIDC.

I will keep watching the sea ice as the summer season develops

MODIS mosaic from the AQUA satellite on 18 November 2017.
MODIS mosaic from the AQUA satellite on 18 November 2017.

** UPDATED 20th November 2017 replacing the first figure from 17  November to 20 November.

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Quick post on the Maud Polynya in the Weddell Sea that I wrote about last week. This is the sea ice data 17 September 2017, and the polynya is both clear and large.

The location of the polynya over Maud Rise. Sea ice data from DMSP SMMI.
The location of the polynya over Maud Rise. Sea ice data from DMSP SMMI.

An enlargement of the polynya shows that it is practically open water.

...continue reading

The sea ice in the Antarctic is at minimum extent in February and expands through to mid September.

This movie shows the Antarctic sea ice extent from 1 Feb to 25 July 2017. The data come from the DMSP SMMI sensor, and it shows the expansion of the sea ice as winter progresses.

 

For me the stand out feature is how late the sea ice expands in the Bellingshausen Sea. I think this is a feature of the super low sea ice last year, and the amount of time it took to lose the extra heat absorbed by the ocean.

The NSDIC data set shows the sea ice is lower than we've seen before by satellite.

Antarctic sea ice extent to 26 July 2017 from NSIDC.
Antarctic sea ice extent to 26 July 2017 from NSIDC.

Currently the Antarctic sea ice extent is ~450 thousand km2 below 1981-2010 median.

~7-8 weeks of sea ice expansion to go.

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The sea ice in the Arctic is at maximum extent in February and retreats through to mid September.

This movie shows the Arctic sea ice extent from 1 Feb to 25 July 2017. The data come from the DMSP SMMI sensor, and it shows the retreat of the sea ice as summer progresses.

You can see from the NSDIC that Arctic sea ice extent is tracking close to the 2012 minimum, and about ~1.6 million km2 below 1981-2010 median.

Arctic sea ice extent to 26 July 2017 from NSIDC.
Arctic sea ice extent to 26 July 2017 from NSIDC.

To see where the sea ice "isn't" you can see the gif I made for a post last week.

The mean Arctic sea ice for the years 1989-93 on 27 July, the sea ice concentration on 27 July 2017 and the difference between the two data sets. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.
The mean Arctic sea ice for the years 1989-93 on 27 July, the sea ice concentration on 27 July 2017 and the difference between the two data sets. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.

In that post I said

Things that stand out for me are the virtually open water in the Barents and Kara Seas.

~6-8 weeks of melt to go...

Today the NASA Earth Observatory Website has published a beautiful image from 29 June 2017 of Hudson Bay in a post called Lingering Sea Ice on Hudson Bay.

Lingering Sea Ice on Hudson Bay
Lingering Sea Ice on Hudson Bay. Image NASA Earth Observatory.

To the untrained eye the sea ice in the bay looks like cloud, but if you look at the still from the movie above on the same day, the sea ice is clear.

Hudson Bay 28 June 2017
Hudson Bay 28 June 2017

The NASA blog post talks about how polar bears were hunting in this sea ice.

 

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I thought it was time to look at the sea ice data as the summer Arctic melt proceeds.

The image below shows the mean sea ice extent 1989-93 on 22 July, the sea ice extent 22 July 2017, and the difference between the two data sets. Reds imply less sea ice than the mean 1989-93, and blues an increased sea ice extent.

The mean Arctic sea ice for the years 1989-93 on 22 July, the sea ice concentration on 22 July 2017 and the difference between the two data sets. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.
The mean Arctic sea ice for the years 1989-93 on 22 July, the sea ice concentration on 22 July 2017 and the difference between the two data sets. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.

As we would expect, compared with the 1989-93 data the sea ice edge is consistently further north. Things that stand out for me are the virtually open water in the Barents and Kara Seas. This region was very slow to freeze over in the autumn and winter of 2016, so I would have expected the sea ice there to be relatively thin at the end of the Arctic winter.

Also the Chukchi Sea is opening.

Overall the area of the Arctic Ocean covered with sea ice is low. Some will note it is currently above the record low in 2012, but it's only 90,000 kmabove that. To me that is not that significant.

Arctic sea ice extent to 22 July 2017 from NSIDC.
Arctic sea ice extent to 22 July 2017 from NSIDC.

What is significant is the sea ice 22 July 2017 is ~1.7 million kmbelow the median extent from 1981-2010.

I looked a couple of days ago at the sea ice in the North West Passage (19 July 2017), and it is starting to open up.

The North West Passage. Image 22 July 2017 from the Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite.
The North West Passage. Image 19 July 2017 from the Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite.

The yellow line traces out possible ship routes through the North West Passage and whilst there is still ~1200 km of sea ice on that route, when you compare the region to the longer term data you can see how low this is compared the historical record.

The difference in the sea ice in the NW Passage on 22 July 2017 compared with the mean for the years 1989-93 on 22 July. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.
The difference in the sea ice in the NW Passage on 22 July 2017 compared with the mean for the years 1989-93 on 22 July. Blue shades imply more sea ice and reds imply decreased sea ice compared with the mean. The original data come from the DMSP SMMI data set at the NSIDC.

It may be this year that the passage may not open at all, but taken together the two plots are a a good example of how we can expect the north west passage to become consistently open as the Arctic continues to warm.