Arctic Sea Ice

PIOMAS October 2018

I was ready to write about this 10 days ago, but the data wasn't out yet. And then life got in the way, as it always does. On the bright side, Wipneus has just updated his PIOMAS graphs to mid-October. More on that below, but first I'll discuss the minimum.

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Another month has passed and so here is the updated Arctic sea ice volume graph as calculated by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the Polar Science Center:

As always, the minimum was reached in September. This year, the lowest amount of sea ice volume, according to PIOMAS, was reached on September 15th, and ended up 6th lowest on record, after 2010, 2011, 2012, 2016 and 2017. And thus, because the maximum was second lowest on record, total melt was 9th lowest on record:

If we look at the data for the end of September, 2018 has already crept to 5th lowest on record, almost on a par with 2017. Where most years gain a bit of volume during September, 2018 actually lost 119 km3, thus reducing the gap with all years that were lower at the end of August (dipping below 2010), as can be seen on this table showing how the differences with previous years have evolved from last month:

If we then look at Wipneus' most recent graph with data up to mid-October, we see that 2018 has gone down even further in the ranking and is now in 3rd place:

Lowest maximum on record (again)

After a drop of almost 262 thousand km2 in just three days, it looks highly likely that the maximum for sea ice extent was reached two weeks ago, according to the data provided by JAXA, the Japan Aerospace Exploration Agency (via ADS-NiPR ; it used to be provided by IJIS).

It's a new lowest maximum record, and the third time in a row that extent stayed below the 14 million km2 mark. The previous lowest max on record was reached in 2015 (13.942 million km2), almost beaten last year (13.959 million km2), but this year SIE went lower still and peaked at 13.878 million km2.

This graph by commenter Deeenngee, posted on the Arctic Sea Ice Forum, visualizes maximums from the past and the trajectory to this year's max:

It looks highly likely that the max has been reached for NSIDC daily SIE as well (graph provided by Jim Hunt from the Great White Con blog), a third record low in a row if my eyes don't deceive me:

The drops are mostly driven by sea ice reductions in the Bering and Okhotsk Seas, but will soon be joined by drops on the Atlantic side of the Arctic as well, as the ice is pretty thin there, according to the Uni Bremen SMOS thin sea ice map.

Given the wind forecast, I also expect further sea ice retreat from the southern shores of Novaya Zemlya (similar to what happened in 2011 and 2012):

PIOMAS December 2016

Another month has passed and so here is the updated Arctic sea ice volume graph as calculated by the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the Polar Science Center:

Well, November definitely was an Oh Jesus-month. Just like during October, the stall in sea ice extent has been reflected in the PIOMAS sea ice volume numbers. The Arctic amassed just 2904 km3 of sea ice, as compared to 3721 km3 for 2012 and 4054 km3 for 2011. The last time a November clocked in less than 3000 km3 was in 2006 (2567 km3), but right now 2016 is more than 4000 km3 lower than 2006, which means there should have been so much more opportunity for expansion. It's just crazy.

And so the differences with previous months have only become larger:

Yes, your eyes are seeing what you think they're seeing: 2016 is 749 km3 lower than 2012, a new record low. Look, here's another visual aid, the volume graph produced by sea ice data virtuoso Wipneus:

Of course, the trend line on the PIOMAS sea ice volume anomaly graph is now firmly lodged in the 2 standard deviation territory:

Melt Pond May 2015

May is the month when melt ponds first start to form on the floes of the Arctic sea ice pack. Melt ponds are important because they soak up more sunlight than the ice would, speeding up the melting process and thus preconditioning the sea ice. When there is lots of melt ponding, something I call melting momentum is built up, sustaining a stable melting rate throughout the rest of the melting season, as we saw in 2011 and 2012. Of course, the reverse is also true, as we saw in rebound years 2013 and 2014.

Because this preconditioning through melt ponds seems to be correlated to the September minimum, scientists are trying to determine the so-called melt pond cover fraction (the percentage of total ice pack area covered by melt ponds) in different ways. Some look at satellite observations, like Anja Rösel from the University of Hamburg did back in 2011, using MODIS satellite data (see here). Others use models, like David Schröder from the University of Reading (see here, and more on that below). Yet others, like Christopher Cox from CIRES, look at radiation data around the Arctic to estimate how much sunlight is reaching the ice pack (I attended Dr. Cox' presentation on this subject at the EGU general assembly this year).

Even though it's very difficult to determine the exact amount and distribution of melt ponds, we can at least compare weather conditions from year to year, as melt ponds come into being due to above freezing temperatures and solar radiation (ie open skies due to high pressure), or a combination of the two. Chris Reynolds has a detailed blog post on atmospheric conditions during all of May on his Dosbat blog, but below I'll be looking at those conditions compared to those of other years during May.

I've divided May up into two halves, and here's the first map showing average temperature anomaly and sea level pressure from May 1st to 15th: 

As can be seen, May started out extremely cold in the Central Arctic Basin, with anomalously warm temps along the coasts of the Beaufort and Kara Seas. Except for 2011, no other year in this comparison was as cold in the heart of the ice pack. In that sense 2015 started out even worse (for melting)  than the two rebound years 2013 and 2014, where a very low melt pond fraction cover during May (and June) made it virtually impossible for those melting seasons to reach the top 5 lowest September minimums.

These extremely low temperatures are also reflected on the DMI graph that shows (modelled) temperatures above 80° latitude:

2013/2014 Winter Analysis

With another interesting freezing season behind us, it's time to compare to previous winters and get an idea of this melting season's foundation. As we have seen in the last two years, the start of the melting season plays an important role, and so it might very well be that the end of the freezing season plays a role as well (what holds for the Arctic summer often is the opposite during winter). If only for the fact that the end of the freezing season is immediately followed by the start of the melting season. Sorry for being so simplistic.

OK, we'll repeat the format from last year and compare the 2013/2014 freezing season with three other freezing seasons. In this case, I have chosen the last three winters (ie preceding the 2011, 2012 and 2013 melting seasons). No 2007? No 2007. I know it's blasphemy, but we have to move on. Click on the images if you want to see a larger version.

Ice age

It's clear that after last year's 'rebound' the Arctic now contains a lot more multi-year ice than in the last 3 years, as can be clearly seen on these AARI ice age maps for the end of April:

2011's vomiting cow doesn't look all that smaller (the brown colour represents the multi-year ice), but this year's genetically modified mouse is still a tad bigger, with a large bulk of multi-year ice taking up position in the Beaufort and even some of the Chukchi Sea. Whether this will prove to be a protective barrier, as witnessed in 2010 and 2011, remains to be seen.

These ASCAT radar images also show that this year the ice pack contains a lot more whiter ice. Here's a comparison for day 109 (April 19th):

Mission possible

The melting season has just about started (no, I'm not calling the max), but already scientists are out there in different parts of the Arctic doing their thing. Currently there are two eye-catching missions being carried out, both having to do with measuring ice thickness to validate satellite data.

The European Space Agency has two simultaneous and overlapping campaigns currently in operation: SMOS ice 2014 and CryoVEx2014. Both missions can be followed on this ESA blog, which contains a lot of interesting information and some awesome images. Take for instance this one:

image courtesy of Stefan Hendricks (AWI)

That's the Norwegian Research Vessel Lance that has left Svalbard last week and is now sailing towards the Barentsz Sea, taking ice thickness measurements along the way using a range of different techniques (including a helicopter).

Notice those melt ponds on the ice, despite the time of year (edit: Stefan Hendricks who took this picture informs me in the comment section below that these are "not melt ponds, but spots of bare thin ice"). Svalbard just experienced the warmest February on record:

A new way of measuring ice thickness

We have a pretty accurate 2D view of the Arctic sea ice, and some clues with regards to its third dimension: thickness. It's the thickness of the ice that determines the influence of atmospheric conditions on the ice pack, and is thus a crucial factor in the amount of sea ice that covers the Arctic Ocean during any given time, especially towards the end of the melting season. But also during the freezing season sea ice thickness plays an important role as an intermediary between sea surface and atmosphere. The thinner the ice is, the more heat and moisture can be transferred from one to the other, which in turn influences atmospheric patterns.

image on the top right, courtesy of NSIDC

The importance of accurate sea ice thickness measurements is not lost on the scientific community. We've had ICESat, we eagerly await the end of the calibration phase of the CryoSat-2 mission, and in the meantime another handy tool for measuring ice thickness has been devised by scientists from the University of Hamburg, using a passive microwave sensor aboard the ESA's Soil Moisture and Ocean Salinity (SMOS) satellite.

images retrieved from the SMOSIce wiki (with permission of L. Kaleschke)

The news was announced two months ago in an ESA press release, but has now been followed up by a research paper that has just been accepted for publication in Geophysical Research Letters: Kaleschke, L., X. Tian-Kunze, N. Maaß, M. Mäkynen, and M. Drusch (2012), Sea ice thickness retrieval from SMOS brightness temperatures during the Arctic freeze-up period.

From the abstract: