Sea ice is still relatively low in both the the Arctic spring and Antarctic autumn. A geographical perspective always helps so here is the status of the sea ice concentration 23 April 2017 for both polar regions.
Here is the sea ice concentration 23 April 2017 compared with the 1989-1993 mean on the 23 April. Red shades = less sea ice than the 1989-93 mean on 23 April, and Blue shades = more sea ice than the 1989-93 mean on 23 April.
The stand out regions for me are once more (as in my post in January), the Northern Barents Sea is relatively low, along with the Bering Sea and the Sea of Okhotsk. There is a consistent retreat of the ice edge almost everywhere, and comparatively a lot of open water in Hudson Bay.
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:
The sea ice around Antarctic is currently still at an historic low. As usual I think it is good to look at a geographic perspective on the sea ice distribution. This is the sea ice concentration 22 January 2017 compared with the 1989-1993 mean on the 22 January.
RED shades = less sea ice than the 1989-93 mean on 22 January.
BLUE shades = more sea ice than the 1989-93 mean on 22 January.
The Amundsen Sea has very low sea ice
Probably for me the most striking feature is the extremely low sea ice concentration from Pine Island Bay through to the Ronne Ice Shelf - this is the Amundsen Sea. We are not going to see much more retreat of of the sea ice in this sector as it has already melted. I think it will stay open water until the freeze up begins some around the end of February. It would have been a great year to do ship based oceanography along that coast. I wonder if their could be an impact on ice shelf melt here. It is possible but as you can see from this article - it is water away from the surface and a few hundred metres deep that is in contact with the glacial ice in the Amundsen Sea Embayment, Overall this has to be a result of the recent El Nino, and is a follow on from the polynya events we saw hear in the late winter.
The Bellingshausen Sea has very relatively high sea ice
In contrast you can see it would not be a good year to be working in the Bellingshausen Sea.
The Weddell Sea ice is at this stage in the summer is compressed against the Antarctic Peninsula. This means that there is heavier sea ice to the close to the Peninsula, and much lower sea ice than expected in the rest of the Weddell Sea. If you look at the MODIS Terra Image you can pick out a very sharp sea ice edge.
Shackleton would have been in trouble this summer if he was heading to Elephant Island.
Towards the annual Antarctic sea ice extent minimum.
We expect the sea ice to reach a minimum towards the end of February. Clearly there are places where there is no more sea ice to melt. Where sea ice is present, it is all down to winds over the next month. If they change and move the pack towards open water then - just as we have seen in the Arctic, the concentration could fall much lower. If the winds continue as they have then we could expect the extent fall to slowly as the seasonal melt continues.
Overall it is still to be likely a record breaking year in the Antarctic sea ice extent record.
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.