After you've read the blog post below, make sure to check out this web page by one of the co-authors of the Nature paper, and also this page with lots of other Arctic sea ice goodies.
A really good paper has been published online a couple of days ago on Nature, called September Arctic sea-ice minimum predicted by spring melt-pond fraction. It's really good because it's interesting, short, and it confirms what I've been suspecting for a while now. And when a paper confirms what one is suspecting, it must be really good, right?
All joking aside, the paper by Schröder et al. presents evidence that melt ponds play a very important role at the start of the melting season, to the point that it can heavily influence the September minimum. The last two melting seasons actually proved to be a great lesson in this respect. 2012 had a really good* start to the melting season, so good that when bad weather showed up, it didn't really slow down sea ice loss, the trend lines just kept dropping (low sea ice volume also played a role, of course). The reverse was true in 2013: cold and cloudy weather during the first half of the melting season caused a lagged response during the short periods when the Sun and higher temps finally got to the ice.
What Schröder et al. did, was develop a melt pond model and incorporate it into the larger Los Alamos sea-ice modelcalled CICE. Here's what they came up with:
I have collected a couple of interesting news articles and interviews over the past few weeks, and now it's time to share with those of you who haven't seen them. I'm posting what I found the most interesting excerpts, follow the links if you want to read the rest.
First up, an interview on SciencePoles with Dr. Agneta Fransson, chemical oceanographer at the Norwegian Polar Institute, called Explaining ocean acidification and consequences for Arctic marine ecosystems:
Are Arctic waters more susceptible to ocean acidification compared to the rest of the world’s oceans? If so, why?
The Arctic Ocean has had high concentrations of CO2 dissolved in it since historical times. This is due to physical processes such as cooling of the relatively fresh surface water, which causes this surface water to sink below the surface towards the bottom of the ocean. When this colder, denser water sinks, it sequesters atmospheric CO2 in the Arctic Ocean. So this results in the Arctic Ocean having a much lower pH and concentrations of carbonate ions (CO32-) compared to other oceans of the world.
The water in the Arctic is also colder. Since CO2 is much more soluble in cold water than it is in warm water, this makes it easier for the ocean to take up more CO2. In addition, as sea ice cover continues to retreat in the Arctic, there will be more open water, which may allow for more direct CO2 uptake into the ocean, and further lowering the ocean’s pH. And, as I mentioned earlier, freshwater influx from rivers empyting into the Arctic ocean, along with melting sea ice, also contribute to lowering the pH of the ocean.
The interview fits in well with this article on other work by the Norwegian Polar Institute that was placed on the website of the Fram Centre. This research is extremely important as ocean heat flux is one of the most influential, but nonetheless relatively poorly understood, factors concerning Arctic sea ice loss.
The article is called New data on Atlantic inflow to the Arctic Ocean reveal effects on sea ice and marine ecosystems:
Tomorrow, April 1st, I'll be doing a short presentation on the Sea Ice Prediction Workshop that will be webcast by UCAR. I'll be talking 10-15 minutes about the ASIB, ASIG and ASIF, and about increasing public interest in Arctic sea ice. You can view the webcast here.
It was always clear how difficult it is to forecast the Arctic sea ice melting season, but this realization reached an even deeper level in the last two years (more about that a couple of paragraphs below). A lot of scientists are working hard to improve the science of predicting the yearly sea ice minimum, and some of them have now evaluated these forecasting efforts, using data from the interagency "system-scale, cross-disciplinary, long-term arctic research program" SEARCH (Study of Environmental Arctic Change) Sea Ice Outlook, which was set up after the drastic sea ice decline of 2007. These monthly SIO predictions have been extensively covered on the ASIB the past 4 melting seasons.
The study by Stroeve et al. (including ASIB guest blogger Larry Hamilton) is called Predicting September Sea Ice Ensemble Skill of the Search Sea Ice Outlook 2008–2013, has just been published in Geophysical Research Letters, and its abstract reads as follows:
Since 2008, the SEARCH Sea Ice Outlook has solicited predictions of September sea ice extent from the Arctic research community. Individuals and teams employ a variety of modeling, statistical and heuristic approaches to make these predictions. Viewed as monthly ensembles each with one or two dozen individual predictions, they display a bimodal pattern of success. In years when observed ice extent is near its trend, the median predictions tend to be accurate. In years when the observed extent is anomalous, the median and most individual predictions are less accurate. Statistical analysis suggests that year-to-year variability, rather than methods, dominate the variation in ensemble prediction success. Furthermore, ensemble predictions do not improve as the season evolves. We consider the role of initial ice, atmosphere and ocean conditions, and summer storms and weather in contributing to the challenge of sea ice prediction.
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:
I blogged about this in 2011 in a post called A warm river runs through it. There are a couple of large rivers that discharge into the Arctic Ocean, such as the Ob, Lena and Yenisei in Russia, and the Mackenzie river in Canada. During spring and summer, these rivers carry warmth from lower latitudes up to the Arctic which helps melting coastal fast ice and sea ice. This impact is on the increase, as the globe continues to warm.
The heat from warm river waters draining into the Arctic Ocean is contributing to the melting of Arctic sea ice each summer, a new NASA study finds.
A research team led by Son Nghiem of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperature of the waters discharging from a Canadian river into the icy Beaufort Sea during the summer of 2012. They observed a sudden influx of warm river waters into the sea that rapidly warmed the surface layers of the ocean, enhancing the melting of sea ice. A paper describing the study is now published online in the journal Geophysical Research Letters.
I distinctly remember discussions here on the ASIB, quite early in the 2012 melting season, with regards to the influence warm Mackenzie water possibly had on the early, massive retreat of sea ice in the Beaufort Sea.
Researchers at the University of Alaska Fairbanks have developed a "web based atlas to let users view historical sea ice data collected between the mid-1800s and today, and compiled for display on an interactive map of the seas surrounding northern Alaska". Here's an overview of all the data sources they used to compile the historical sea ice atlas.
More background info in this Alaska Dispatch article:
New sea ice map offers a long-term look at climate change
Mining more than a century of sea ice observations, including from 19th century Yankee whalers and 20th century Arctic wildcatters, researchers at the University of Alaska Fairbanks have put together an expansive view of climate change that lets web surfers track the ice pack off Alaska for decades.
To create the play-by-play of diminishing sea ice, researchers relied on space-age data -- satellite images collected since 1979 -- plus decades of older information collected from ship decks, shorelines and airplanes.
After this 2012 blog post on Arctic pollution, it's time to return to the subject, if only because Arctic sea ice is proving to be a significant factor in changes in atmospheric chemistry, leading to increases in mercury concentrations in the Arctic. This happens through sea ice melting during summer, and an increase in leads and cracks during winter.
In the past couple of days two papers were published that show the relationships. The first, Convective forcing of mercury and ozone in the Arctic boundary layer induced by leads in sea ice by Moore et al., was published in Nature and deals with bromine. This Science Daily article explains it well:
Cracked Sea Ice Stirs Up Arctic Mercury Concern
Image credit: University of Hamburg, Germany
Jan. 15, 2014 — Vigorous mixing in the air above large cracks in Arctic sea ice that expose seawater to cold polar air pumps atmospheric mercury down to the surface, finds a NASA field campaign. This process can lead to more of the toxic pollutant entering the food chain, where it can negatively affect the health of fish and animals who eat them, including humans.
Scientists measured increased concentrations of mercury near ground level after sea ice off the coast of Barrow, Alaska, cracked, creating open seawater channels called leads. The researchers were in the Arctic for the NASA-led Bromine, Ozone, and Mercury Experiment (BROMEX) in 2012.
"None of us had suspected that we would find this kind of process associated with leads," said Son Nghiem, a scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Nghiem is the BROMEX principal investigator and a coauthor of a paper reporting the discovery published in Nature on Jan. 15.
The mercury-pumping reaction takes place because open water in a lead is much warmer than the air above it, according to study lead author Chris Moore of the Desert Research Institute, Reno, Nev. Because of that temperature difference, the air above the lead churns like the air above a boiling pot. "The mixing is so strong, it actually pulls down mercury from a higher layer of the atmosphere to near the surface," Moore said. The mixing, marked by dense clouds spewing out of the leads, extends up into the atmosphere about a quarter-mile (400 meters). Moore estimates this may be the height where the mercury pumping occurs.
Almost all of the mercury in the Arctic atmosphere is transported there in gaseous form from sources in areas farther south. Scientists have long known that mercury in the air near ground level undergoes complex chemical reactions that deposit the element on the surface. Once the mercury is completely removed from the air, these reactions stop. However, this newly discovered mixing triggered by leads in the sea ice forces down additional mercury to restart and sustain the reactions.
Leads have become more widespread across the Arctic Ocean as climate change has reduced Arctic sea ice cover. "Over the past decade, we've been seeing more new sea ice rather than perennial ice that has survived for several years. New ice is thinner and saltier and cracks more easily. More new ice means more leads as well," said Nghiem.
Read the rest of the article here, or the press release at NASA JPL.
The second study, High levels of molecular chlorine in the Arctic atmosphere by Liao et al., was published in Nature Geoscience and deals with chlorine. For a background story we turn to the Georgia Tech News Center:
We have monthly PIOMAS updates, a new sea ice thickness product derived from SMOS brightness temperatures was presented earlier this month (see video), and now it's time for some more news from the third of the thickness trident: CryoSat-2.
Measurements from ESA’s CryoSat satellite show that the volume of Arctic sea ice has significantly increased this autumn.
The volume of ice measured this autumn is about 50% higher compared to last year.
In October 2013, CryoSat measured about 9000 cubic km of sea ice – a notable increase compared to 6000 cubic km in October 2012.
Over the last few decades, satellites have shown a downward trend in the area of Arctic Ocean covered by ice. However, the actual volume of sea ice has proven difficult to determine because it moves around and so its thickness can change.
CryoSat was designed to measure sea-ice thickness across the entire Arctic Ocean, and has allowed scientists, for the first time, to monitor the overall change in volume accurately.
About 90% of the increase is due to growth of multiyear ice – which survives through more than one summer without melting – with only 10% growth of first year ice. Thick, multiyear ice indicates healthy Arctic sea-ice cover.
This year’s multiyear ice is now on average about 20%, or around 30 cm, thicker than last year.
There were fewer snow and ice extremes than in 2012. Many regions and components of the Arctic environment were closer to their long-term averages, but the effects of a persistent warming trend that began over 30 years ago remain clearly evident.
The impacts of the warming climate on the physical environment during those 30 years are influencing Arctic ecosystems on the land and in the sea.
Here's a video accompanying the report:
And a longer video showing the press conference announcing the report at the 2013 AGU Fall Meeting, last Thursday:
Climate Central's Andrew Freedman, who was present at the press conference to ask questions, has another excellent summary of the report here.