Tag Archives: Antarctic

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The Arctic

It's been quite a year in the Arctic. Over the winter 2015/6 we had the strongest and coldest Arctic polar vortex of the last 68 years. This contributed to a low maximum in Arctic sea ice extent. At that stage only the locals and the scientists were looking, and I wrote about this in a blog post called Arctic sea ice 2016. This was followed by the joint second lowest Arctic summer sea ice extent.

Unusual weather in the early winter led to records being broken and the sea ice the Arctic sea has been the lowest recorded in the satellite record for the time of year.

Where are we at the Northern winter solstice?

The mean Arctic sea ice for the years 1989-93 on 21 December, the sea ice concentration on 21 December 2016 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 21 December, the sea ice concentration on 21 December 2016 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 ice edges have retreated compared with 1989 - but as I wrote about in Record Low Arctic Sea Ice Extent we still have the very low sea ice concentration in the Barents Sea. There is also  still a very low concentration region north of the Bering Strait but the the Chukchi Sea and Hudson Bay have mostly frozen over.

...continue reading

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The sea Ice is too heavy for the RRS James Clark Ross to make Rothera base right now. You may have thought the sea ice on the satellite images didn't look too bad, but it's all about how thick the sea ice is, and where the open water is.

To quote the radio officer Mike Gloistein:

The sea-ice around the bottom of Adelaide Island has been heavy and whilst (for those of you who look at the satellite pictures) there are some leads and areas of open water,  they are close to land and if we took that route (which also includes shallow water and rocks) and the weather then pushed the ice inland,  the ship could easily become stuck between a rock and a hard place.

And then the ship could get seriously stuck just like I said the John Biscoe did in my previous post. In that case the ship was rescued by Polarstern.

This was the satellite image I posted yesterday:

The MODIS satellite image off Adelaide Island 25 Nov 2016, with the location of the RRS James Clark Ross 0000 28 November 2016.
The MODIS satellite image off Adelaide Island 25 Nov 2016, with the location of the RRS James Clark Ross 0000 28 November 2016.

And this is a navigation chart of that region.

Section of the Navigation Chart around the southern tip of Adelaide Island.
Section of the Navigation Chart around the southern tip of Adelaide Island.

The light blue shading is shallow water and it's not a great place for a ship to go without freedom of navigation. The sea ice takes away that freedom. This is of course a very sensible choice by the ships Master, and exactly the same thing happened to a voyage I was on in 2004.

In another few weeks it will be clear for them.

I don't think this was predictable. You really have to be on the ground to see what the conditions are to make a call on whether it is safe or not. Two months ago on the 6 October I blogged about the sea ice and the potential of this happening, and said:

There are a lot of Antarctic research stations on the west of the Antarctic Peninsula, including Rothera, the largest British Base.  If the winds maintain the westerly direction then I can imagine it could be slow to resupply the base this season. There is time for it to change. According to the published schedule the ship is not due to arrive until 27 November 2016.

A slow resupply is not uncommon and I have been on at least one unsuccessful resupply voyage in my career. I took the picture below on 11 December 2004 under similar conditions.

James Clark Ross making very slow progress in compressed sea ice in Marguerite Bay, the Western Antarctic Peninsula.
James Clark Ross making very slow progress in compressed sea ice in Marguerite Bay, the Western Antarctic Peninsula.

Although it is not predictable, the fantastic British Antarctic Survey Operations will have planned for the consequences.

For a last point on the left of the navigational chart is one of my favourite place names:

Fullastern Rock to the west of Adelaide Island
Fullastern Rock to the west of Adelaide Island

As it says on the UK Antarctic Place Names website:

Fullastern Rock (67° 36′ 58″ S, 69° 25′ 59″ W) is a submerged rock on the west side of Johnston Passage, to the west of Adelaide Island. It was first charted by a Royal Navy Hydrographic Survey Unit from RRS John Biscoe in 1963.  The ship was compelled to go full astern to avoid this hazard  – a story succinctly captured by this evocative name!

 

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This is the the full years data to 21 November for the anomalies of the sea ice extent in 2016. See my blog post Antarctic sea ice 2016: Historic lows for full context.

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.

The five year average sea ice extent - the extent for the same day in 2016. Red colours indicate less sea ice than the 5 year mean.
The five year average sea ice extent (1989-93) - the extent for the same day in 2016. Red colours indicate less sea ice than the 5 year 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.

A post describing this data is Antarctic sea ice 2016: Historic lows

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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.

The annotated seasonal extent of sea ice in the Southern hemisphere. From Tamino's post Sea Ice, North and South.
The annotated seasonal extent of sea ice in the Southern hemisphere. From Tamino's post Sea Ice, North and South.

From January up to September the sea ice extent in 2016 follows all previous data.

But what happened in September?

...continue reading

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My previous posts on Amundsen Sea Polynya and their development showed ~37,600 km2 of open water in front of the ice shelves. It is very early spring in Antarctica at this time of the year and it’s still cold.

That means sea ice can still grow.

This is the Dotson Getz polynya on 9 October 2016. It has a perimeter of ~800 km and an area of ~25,500 km2.

The Dotson Getz polynya on 9 October 2016. Open water is black and streaks of sea ice growth are clear. The location of the Bear Peninsula Automatic Weather Station is marked.
The Dotson Getz polynya on 9 October 2016. Open water is black and streaks of sea ice growth are clear. The location of the Bear Peninsula Automatic Weather Station is marked.

I put together the satellite data from 9-12 October 2016 and it shows extremely rapid sea ice growth.

...continue reading

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I noticed in a blog post last week that there was a finger of open water extending down the Western Weddell Sea. I've carried on watching this open water in the MODIS satellite data. Whilst it's been opening and closing, there is a lot of open water. It's clearly a major sea ice generating factory at the moment.

MODIS image of the Western Weddell Sea 30 September 2016. The Open Water is clear.
MODIS image of the Western Weddell Sea 30 September 2016. The Open Water is clear.

The open water is clear in the lower resolution passive microwave sea ice data too.

The sea ice extent along the Antarctic Peninsula 2 October 2016. Data from DMSP SSMI
The sea ice extent along the Antarctic Peninsula 2 October 2016. Data from DMSP SSMI

If you look at some model output there are air temperatures above this open water of between -10° to about -25°C.

Surface temperature at 2m from NCEP output. 3 October 2016.
Surface temperature at 2m from NCEP output. 3 October 2016. From Climate Reanalyzer.org

What is really good is if you look at the temperature anomaly (i.e. the departure from the average with a 1979-2000 baseline), it is very warm over the Weddell Sea.

The temperature departure from average for NCEP output 3 October 2016. Image from climateReanalyzer.org.
The temperature departure from average for NCEP output 3 October 2016. Image from climateReanalyzer.org.

I think the reason it is warmer is because the Weddell Sea pack ice is looser this year. So (as you can see in the picture above) there is lots of open water. The atmosphere is being warmed by the ocean as the sea ice is being generated.

Another pointer to the pack being looser this year is that in August 2016 in the Eastern Weddell Sea there was a rare sighting of the Weddell Polynya.

The Weddell Polynya as observed on 14 August 2016 in passive satellite data.
The Weddell Polynya as observed on 14 August 2016 in passive satellite data. It is a polynya with its own wikipedia page.

I think the Weddell Sea pack ice is more mobile this winter. This is also telling us something about the difference between sea ice extent and sea ice thickness. The sea ice extent is large and easy to measure in the Antarctic - but we don't know how thick it is.

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Just noticed this on the MODIS  sensor on the TERRA satellite image from 10 September 2016.  (Tile Antarctica_rc05c01 if you are interested in that sort of thing)

Antarctic Sound on the tip of the Antarctic Peninsula 10 Sept 2016
Antarctic Sound on the tip of the Antarctic Peninsula 10 Sept 2016

The Antarctic sea ice ice extent map for 10 September 2016 shows an interesting and large low concentration right at the tip of the Antarctic Peninsula

The sea ice extent around Antarctic 10 September 2016. Yellow box is roughly where the MODIS image is, and Antarctic Sound is labelled. Data from DMSP SMMI
The sea ice extent around Antarctic 10 September 2016. Yellow box is roughly where the MODIS image is, and Antarctic Sound is labelled. Data from DMSP SMMI

So why the missing sea ice at the top of the Peninsula?  It could be a storm, or could be heat from the ocean keeping the area ice free. I'll have a look at the data when I've time, but for now I would bet on the ocean.

Interestingly historically it has been a bit of a tough place. Otto Nordenskjöld navigated the sound in December 1902 on the Swedish Antarctic Expedition before their ship, the Antarctic was crushed and lost. They were stranded for two years...

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This just on twitter from the UK Ministry of Defence about the recent magnificent voyage of HMS Protector.

The Tweet posted by MOD on 18th Jan 2016
The Tweet posted by MOD on 18th Jan 2016

On the web page in the link it says

By visiting this region Protector achieved a latitude of 77 Degrees 56 Minutes South – the very edge of the vast Ross Ice Shelf, named for James Clark Ross who led the exploration of the area.

No official British ship has been this far south since 1936 and it is believed not since James Clark Ross’s own expedition in 1842.

I don't think this is true. The British Antarctic Survey Ship RRS Bransfield reached likely a little further south. According to this note from the Second Officer Chris Elliot which is published on the website The LOFTSMAN which is about the shipyards of Leith.

Furthest South of the RRS Bransield was 77 56' 44''
Furthest South of the RRS Bransield was 77 56' 44''

RRS Bransfield reached 77°56' 44"S.

So 44 seconds further south than HMS Protector.

Which is what? 1.3 km?

I know it's not much further south and Protector likely matched it (they don't give their decimal). I just wanted to make the point that it is close. Very close.

The second officer in the note - Chris Elliot went on to become the Captain of the RRS John Biscoe, and then he was a member of the team that built the RRS James Clark Ross for many years, before becoming one of the Captains of that great ship.

UPDATE See comment below by Radio Officer of the RRS James Clark Ross Mike Gloistein.

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This plot shows the Antarctic sea ice extent, the Arctic sea ice extent, and the total sea ice extent plotted against time.

Arctic, Antarctic and total sea ice extent 2012

Like in previous post I chose 2012 only because it is the most recent complete year in this data set.

Take a look at the minimum, the maximum and the range of the sea ice extent.

Antarctic: Minimum Antarctic sea ice extent 3.11 x 106 km2
Maximum Antarctic sea ice extent 19.48 x 106 km2
Range of the Antarctic sea ice extent 16.37 x 106 km2
Arctic: Minimum Arctic sea ice extent 3.37 x 106 km2
Maximum Arctic sea ice extent 15.25 x 106 km2
Range of the Arctic sea ice extent 11.88 x 106 km2

The range of Antarctic sea ice extent is 16.37 x 106 km2, and the range of the Arctic sea ice extent is 11.88 x 106 km2.

The Antarctic and the Arctic do not "balance" in sea ice extent - the Antarctic variations are much larger.

Look at the shape of the annual cycle. I said previously that in the Antarctic the seasonal cycle of sea ice extent is not symmetrical. Sea ice grows slowly and steadily before decaying relatively rapidly: the melt period is shorter than the growth period.

In the Arctic the time sea ice grows is roughly similar to the time sea ice melts.

So they do not "balance". The seasonal cycles, ranges, minimums and maximums are  different,

The annual cycle of the Arctic and Antarctic sea ice extent is very different.

We know that the extent and thickness of the Arctic sea ice is decreasing. See for example what Tamino wrote in Feb 2014.

But what about the Antarctic? The extent of the sea ice has broken records for the satellite era. (This is a very funny article making some claims about what that means - if you want a clue what is the difference between glacial ice and frozen sea water?).

Some believe the observed reduction in the Arctic sea ice volume is balanced by the increase in the Antarctic sea ice extent. So we should look at the black line in the plot above.

I will get onto why I don't think that is a good idea in a coming post.

Here is the plot animated with 1 second = 10 days

 About the data

The data set is from the National Snow and Ice Data Center Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data.