Arctic Sea Ice

Arctic sea ice loss and the role of AGW

I like to think that it's pretty obvious that AGW has something to do with the rapid loss of Arctic sea ice. Or to quote Dr Jennifer Francis: How could it not? However, to prove it scientifically is another matter entirely. Dirk Notz and Jochem Marotzke from the Max Planck Institute for Meteorology have given it a shot. (image credit: Dirk Notz / MPI for Meteorology)

From ScienceDaily (hat-tip to the Yooper):

Arctic Sea-Ice Loss Didn't Happen by Chance

ScienceDaily (May 2, 2012) — The ongoing rapid retreat of Arctic sea ice is often interpreted as the canary in the mine for anthropogenic climate change. In a new study, scientists have now systematically examined the validity of this claim. They find that neither natural fluctuations nor self-acceleration can explain the observed Arctic sea-ice retreat. Instead, the recent evolution of Arctic sea ice shows a strong, physically plausible correlation with the increasing greenhouse gas concentration. For Antarctic sea ice, no such link is found -- for a good reason.

When scientists try to attribute some observed climatic change to a specific forcing, they usually use complex climate models. The scientists at Germany's Max Planck Institute for Meteorology (MPI-M), however, decided on a different strategy as they set out to identify the main driver for the observed sea-ice loss in the Arctic. Dirk Notz, lead author of the study that was now published in the journal Geophysical Research Letters, explains why: "Sea ice is so thin that it reacts very sensitive to the large natural fluctuations of weather and climate that prevail in the Arctic. Because these fluctuations are inherently chaotic, their specific timing cannot be reproduced by standard climate models. Such models therefore aren't necessarily the best tool to examine if natural fluctuations did cause the observed sea-ice loss."

(...)

"In the end, only the increase in greenhouse gas concentration showed a physically plausible link with the observed sea-ice retreat. We expect a decreasing sea-ice cover for increasing greenhouse gas concentration, which is exactly what is observed," Notz explains. The physical link between greenhouse gas concentration and sea ice is quite straightforward, he adds: "Greenhouse gases increase the downwelling thermal radiation. This radiation, in turn, is the major player in the heat budget of Arctic sea ice."

Read the whole thing here. Paper available here.

GlobIce: mapping the movement of sea ice

This comes from a press release by University College London:

14 March 2012

A UCL-led project to map changes in sea ice in the Arctic has released its data after the conclusion of the 5 year project. 

Available for use in climate models by scientists and partner institutions such as the UK Met Office, the data could help improve current climate models. 

Launched in 2005 with a consortium of eight partners led by UCL, the aim of the €1 million GlobIce project was to measure sea ice motion for use in climate modelling and research.

Sea ice profoundly affects the exchanges of heat, water and momentum between the ocean and atmosphere, and plays an important role in oceanic convection and deep-water formation.  

“The data which the GlobIce system can provide is essential to understanding the dynamics of the rapidly changing sea ice cover in the Arctic,” said Dr Seymour Laxon (UCL Centre for Polar Observation and Modelling).

Using radar images of ice displacement determined at intervals of a few days, the team, which included engineers and project managers at the UCL Mullard Space Science Laboratory, used the images to generate a large number of high-resolution products useful for climate research, such as sea ice velocity maps.

Continue reading here...

The ESA press release also has nice animations.

WACC overview

I've planning to write about this for ages, but hibernation and life in general always get in the way. Never mind the fact that it's a complex subject, surrounded on all sides by uncertainty. But why burden yourself with a (seemingly) herculean task, when others have already written about it so eloquently, and explained it so well?

WACC stands for Warm Arctic Cold Contintents, and refers to blocking patterns that cause outbursts of cold air to spill out from the Arctic and cause extreme winter conditions further down on the Northern Hemisphere (image on the right found here). The theory is that these blocking patterns are in turn caused by a breakdown in the Polar Vortex, due to a combination of Arctic amplification, autumnal snow cover increase and sea ice retreat (particularly in the Barentsz and Kara Sea).

Here are some research papers on the subject, the most recent of which received quite a bit of media attention in the past few months:

Small research paper database

I have tried to postpone this as much as possible, but studying the Arctic and its sea ice forces you sooner or later to start reading actual research papers. So far I had been saving PDFs in a folder, but I figured it'd be much better to incorporate them somewhere in the Arctic Sea Ice blog. And so I have started a subsection to collect and discuss Arctic-related research papers that pertain to different categories (see image on the right).

You reach the category page by clicking 'papers' in the navigation bar. Clicking on one of the categories takes you to a list of research papers in that particular category. You can add comments to the category page and suggest research papers you think fit in well. Clicking on the discussion page of a research paper takes you to a page with all the info on the paper (author, journal, date of publication), the abstract, and excerpts I think are interesting. You can add comments to the discussion page if you'd like to discuss the research paper.

So far I have only included two research papers as an example (in the Atmospheric Patterns and Oceanic Patterns sections). I will try and add one research paper per week on average, mostly seminal papers or papers that are cutting edge and groundbreaking. It should make a nice collection after a year or so and I hope it will turn out to be useful (because it's a lot of work). Let me know if I'm doing something illegal before suing me!

Arctic Report Card 2011

NOAA has released the Arctic Report Card 2011 (h/t Peter Sinclair):

 

Atmosphere - Higher temperatures in the Arctic and unusually lower temperatures in some low latitude regions are linked to global shifts in atmospheric wind patterns.

Sea Ice & Ocean - A shift in the Arctic Ocean system since 2007 is indicated by the decline in ice age and summer extent, and the warmer, fresher upper ocean.

Marine Ecosystems - Since 1998, biological productivity at the base of the food chain has increased by 20%. Polar bears and walrus continue to lose habitat in Alaskan waters.

Terrestrial Ecosystems - Increased “greenness” of tundra vegetation in Eurasia and North America linked to increase in open water and warmer land temperatures in coastal regions.

Hydrology and Terrestrial Cryosphere - Continued dramatic loss of ice sheet and glacier mass, reduced snow extent and duration, and increasing permafrost temperatures are linked to higher Arctic air temperatures.

New paper by Polyakov, Kwok and Walsh

A new paper by a few very well-known sea ice experts called Recent changes of arctic multiyear sea-ice coverage and the likely causes has appeared as an early online release, a "preliminary PDF of the author-produced manuscript that has been peer-reviewed and accepted for publication" in the Bulletin of the American Meteorological Society.

I don't have the time right now to go through this paper, but I'm putting this post up so the finer points and implications of this paper can be discussed.

Figure 1. Satellite-based Arctic Ocean multiyear ice (MYI) coverage. Composite time series shows MYI area on January 1 each year. Maps show fraction (part of a unit) of MYI. Adapted from Kwok and Untersteiner (2011).

From the paper's conclusion:

This article addresses probable causes of the observed reduction of the Arctic Ocean's coverage of MYI over that past decade. There is evidence of the increasingly important role of atmospheric thermodynamic forcing in shaping recent changes of the Arctic MYI. In addition to direct MYI melt due to high-latitude warming, the impact of enhanced upper ocean solar heating through numerous leads in decaying Arctic ice cover and consequent ice bottom melting has resulted in an accelerated rate of sea-ice retreat via a positive ice-albedo feedback mechanism. The pan-Arctic role of this feedback is yet to be quantified. Analysis of satellite ice motion suggests that the role of ice export through straits connecting the Arctic Ocean with sub-polar basins may be elusive. This situation probably differs from the situation that existed in the early to mid-1990s, when enhanced ice export through Fram Strait was caused by anomalous winds associated with the positive Arctic Oscillation phase. The possible long-lasting impact of anomalous winds such as those in 2004–05 or 2007 (especially when superimposed on a warming trend) on the state of MYI should not be ruled out. An intriguing feature of the scenario described here is the potential contribution of oceanic thermodynamic forcing to the recent changes of the high-latitude MYI coverage. Available observations suggest a thermodynamic coupling between the heat of the ocean interior and the sea ice. In the Canadian Basin, the impact of Pacific water warmth has been recently documented. While vertical AW heat fluxes are negligible in the Canadian Basin, turbulent mixing may be strong enough in the western Nansen Basin to produce a sizeable effect of AW heat on sea ice. In the eastern Eurasian Basin, double diffusion provides an important alternative to weak turbulent mixing for upward AW heat transport. However, this contribution to sea-ice loss remains uncertain pending new field experiments that will provide estimates of upward AW heat fluxes.

The fact that the rate of MYI recovery observed in recent years shows a delay relative to thermodynamic forcing indicates that MYI is resistant to recovery. However, the relative roles of dynamic and thermodynamic factors in recent changes of the Arctic MYI cover remains to be determined. Quantifying these roles is a high priority if we are to develop reliable forecasts of the future state of Arctic ice coverage.

Polar ice caps can recover

More news from Arctic sea ice GCMs, scientifically interesting though perhaps less stimulating than the recent Funder et al and Kay et al studies (hat-tip Bob Wallace). From Science Daily:

Polar Ice Caps Can Recover from Warmer Climate-Induced Melting, Study Shows

A growing body of recent research indicates that, in Earth's warming climate, there is no "tipping point," or threshold warm temperature, beyond which polar sea ice cannot recover if temperatures come back down. New University of Washington research indicates that even if Earth warmed enough to melt all polar sea ice, the ice could recover if the planet cooled again.

In recent years scientists have closely monitored the shrinking area of the Arctic covered by sea ice in warmer summer months, a development that has created new shipping lanes but also raised concerns about humans living in the region and the survival of species such as polar bears.

In the new research, scientists used one of two computer-generated global climate models that accurately reflect the rate of sea-ice loss under current climate conditions, a model so sensitive to warming that it projects the complete loss of September Arctic sea ice by the middle of this century.

However, the model takes several more centuries of warming to completely lose winter sea ice, and doing so required carbon dioxide levels to be gradually raised to a level nearly nine times greater than today. When the model's carbon dioxide levels then were gradually reduced, temperatures slowly came down and the sea ice eventually returned.

Arctic ice melt could pause in coming decades

First the ice extent had been 50% less during the Holocene Climatic Optimum than it was in September 2007, now we have models saying the ice could expand during some decades just as easily as contract, according to this NSF press release (hat-tip to Noel):

Researchers find unexpected results in study of ice cover in the Arctic

Despite the rapid retreat of Arctic sea ice in recent years, the ice may temporarily stabilize or somewhat expand at times over the next few decades, new research indicates.

Results of a study by scientists at the National Center for Atmospheric Research (NCAR) appear this week in the journal Geophysical Research Letters (GRL), published by the American Geophysical Union.

The National Science Foundation (NSF), NCAR's sponsor, funded the work.

"As we learn more about climate variability, new and unexpected research results are coming to light," says Sarah Ruth, program director in the Division of Atmospheric and Geospace Sciences, which funds NCAR for NSF. "What's needed now are longer-term observations to better understand the effect of climate change on Arctic sea ice."

The computer modeling study reinforces previous findings by other researchers that the level of Arctic sea ice loss observed in recent decades cannot be explained by natural causes alone, and that the ice will eventually melt away during summer if the climate continues to warm.

But in an unexpected new result, the NCAR research team found that Arctic ice under current climate conditions is as likely to expand as it is to contract for periods of up to about a decade.

Arctic 'tipping point' may not be reached

I saw this news item in the blog news feed in the right side bar and thought it was worth a post. From the BBC website:

Arctic 'tipping point' may not be reached

By Matt McGrath Science reporter, BBC World Service

Scientists say that current concerns over a tipping point in the disappearance of Arctic sea ice may be misplaced.

Danish researchers analysed ancient pieces of driftwood found in Northern Greenland which they say is an accurate way of measuring the extent of the ancient ice loss.

Writing in the journal Science, the team found evidence that sea ice levels were about 50% lower than today when temperatures warmed around 5,000 years ago.

They argue that a tipping point under current scenarios is unlikely, as changes to wind systems can slow down the rate of melting.

New paper from Maslanik et al.

I'm going to try and regularly report on new scientific papers that discuss some aspect or other of Arctic sea ice. Creating a special segment on the blog that categorizes all important research papers (a bit like the AGW Observer blog) is still on my to-do list.

Following yesterday's blog post that referred to Chris R's blog where he devotes several posts to multiyear ice, I now call attention to a new paper by Maslanik, Stroeve, Fowler and Emery called Distribution and trends in Arctic sea ice age through spring 2011, which was published in Geophysical Research Letters on July 14th.

From the abstract:

Analysis of a satellite-derived record of sea ice age for 1980 through March 2011 shows continued net decrease in multiyear ice coverage in the Arctic Ocean, with particularly extensive loss of the oldest ice types. The fraction of total ice extent made up of multiyear sea ice in March decreased from about 75% in the mid 1980s to 45% in 2011, while the proportion of the oldest ice declined from 50% of the multiyear ice pack to 10%. These losses in the oldest ice now extend into the central Arctic Ocean and adjacent to the Canadian Archipelago; areas where the ice cover was relatively stable prior to 2007 and where long-term survival of sea ice through summer is considered to be most likely. Following record-minimum multiyear ice coverage in summer 2008, the total multiyear ice extent has increased to amounts consistent with the negative trend from 2001–2006, with an increasing proportion of older ice types. This implies some ability for the ice pack to recover from extreme conditions. This recovery has been weakest in the Beaufort Sea and Canada Basin though, with multiyear ice coverage decreasing by 83% from 2002 to 2009 in the Canada Basin, and with more multiyear ice extent now lost in the Pacific sector than elsewhere in the Arctic Ocean.