The meltdown has not been as dire as some would suggest, said geophysicist Christian Haas of the University of Alberta. His international team flew across the top of the planet last year for the 2,412-kilometre survey.

They found large expanses of ice four to five metres thick, despite the record retreat in 2007.

“This is a nice demonstration that there is still hope for the ice,” said Haas.

The survey, which demonstrated that the “bird” probe tethered to a plane can measure ice thickness over large areas, uncovered plenty of resilient “old” ice from Norway to the North Pole to Alaska in April 2009.

The thickness had “changed little since 2007, and remained within the expected range of natural variability,” the team reports in the Geophysical Research Letters.

Read more in the Ottawa Citizen: Scan of Arctic ice dispels melting gloom: Researcher

Synoptic airborne thickness surveys reveal state of Arctic sea ice cover

Christian Haas

Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada

Stefan Hendricks

Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

Hajo Eicken

Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA

Andreas Herber

Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany

While summer Arctic sea‐ice extent has decreased over the past three decades, it is subject to large interannual and regional variations. Methodological challenges in measuring ice thickness continue to hamper our understanding of the response of the ice‐thickness distribution to recent change, limiting the ability to forecast sea‐ice change over the next decade. We present results from a 2400 km long pan‐Arctic airborne electromagnetic (EM) ice thickness survey in April 2009, the first‐ever large‐scale EM thickness dataset obtained by fixed‐wing aircraft over key regions of old ice in the Arctic Ocean between Svalbard and Alaska. The data provide detailed insight into ice thickness distributions characteristic for the different regions. Comparison with previous EM surveys shows that modal thicknesses of old ice had changed little since 2007, and remained within the expected range of natural variability.

Citation: Haas , C., S. Hendricks, H. Eicken, and A. Herber (2010), Synoptic airborne thickness surveys reveal state of Arctic sea ice cover, Geophys. Res. Lett., 37, L09501, doi:10.1029/2010GL042652.

Early in March, Arctic sea ice appeared to reach a maximum extent. However, after a short decline, the ice continued to grow. By the end of March, total extent approached 1979 to 2000 average levels for this time of year. The late-season growth was driven mainly by cold weather and winds from the north over the Bering and Barents Seas. Meanwhile, temperatures over the central Arctic Ocean remained above normal and the winter ice cover remained young and thin compared to earlier years.

NSIDC: Cold snap causes late-season growth spurt

Returning ice – after years of declining cover – has astonished climate scientists who blamed unusually cold weather over the Bering Sea.

Researchers said they recorded the most ice in March since 2001 – and that the cover is approaching long-term average levels for the first time in ten years.

The scientists who released the data stressed that last month’s rise was part of yearly variations in ice cover and could not be taken as a sign that global warming is coming to an end.

But sceptics argued that the findings undermined ‘alarmist’ claims that the North Pole could be free of summer ice by 2013.

Read more in the Daily Mail: Increase in Arctic ice confounds doomsayers – but does not spell the end of global warming, scientists warn

Source: National Snow and Ice Data Centre (NSIDC)

Ice blown out of the region by Arctic winds can explain around one-third of the steep downward trend in sea ice extent in the region since 1979, the scientists say.

The study does not question that global warming is also melting ice in the Arctic, but it could raise doubts about high-profile claims that the region has passed a climate “tipping point” that could see ice loss sharply accelerate in coming years.

The new findings also help to explain the massive loss of Arctic ice seen in the summers of 2007-08, which prompted suggestions that the summertime Arctic Ocean could be ice-free withing a decade. About half of the variation in maximum ice loss each September is down to changes in wind patterns, the study says.

Guardian.co.uk: Wind contributing to Arctic sea ice loss, study finds

Ogi, M., K. Yamazaki, and J. M. Wallace (2010), Influence of winter and summer surface wind anomalies on summer Arctic sea ice extent, Geophys. Res. Lett., doi:10.1029/2009GL042356, in press.

Most measures of palaeoclimate provide data on only average annual temperatures, says William Patterson, an isotope chemist at the University of Saskatchewan in Saskatoon, Canada, and lead author of the study1. But molluscs grow continually, and the levels of different oxygen isotopes in their shells vary with the temperature of the water in which they live. The colder the water, the higher the proportion of the heavy oxygen isotope, oxygen-18.

The study used 26 shells obtained from sediment cores taken from an Icelandic bay. Because clams typically live from two to nine years, isotope ratios in each of these shells provided a two-to-nine-year window onto the environmental conditions in which they lived.

Patterson’s team used a robotic sampling device to shave thin slices from each layer of the shells’ growth bands. These were then fed into a mass spectrometer, which measured the isotopes in each layer. From those, the scientists could calculate the conditions under which each layer formed.

“What we’re getting to here is palaeoweather,” Patterson says. “We can reconstruct temperatures on a sub-weekly resolution, using these techniques. For larger clams we could do daily.”

The data shows the Roman Warm Period, a cooling in the Dark Ages, the Medieval Warm Period, and the Little Ice Age.

All we need now is for ‘Michael Clam’ to use his special methodology in order to create a straightish line, and then add some instrumental data in order to create a ‘hockey stick.’

An extract from the actual paper says:

The interval from ∼230 B:C: to A.D. 40 was one of exceptional warmth in Iceland, coinciding with a period of general warmth and dryness in Europe known as the Roman Warm Period, from ∼200 B:C: to A.D. 400 (23). On the basis of δ18O data,reconstructed water temperatures for the Roman Warm Period in Iceland are higher than any temperatures recorded in modern times.

That should provide some comfort for those who worry about the current Arctic warming and sea ice etc.

The Nature News article concludes:

One can envision a tree-ring-like continuous history, given a lot more effort. If he can find the funding, that is exactly what Patterson would like to establish next. “We have what may be the world’s oldest clam,” he says, “that might give a continuous record going back 400 years.” He also wants to push the study back towards the end of the last ice age. “We have 11,000 years worth of material,” he says.

Two millennia of North Atlantic seasonality and implications for Norse colonies

Patterson, W. P., Dietrich, K. A., Holmden, C. & Andrews, J. T. Proc. Natl Acad. Sci. USA doi: 10.1073/pnas.0902522107 (2010).

Abstract:

δ18O values of mollusks recovered from near-shore marine cores in
northwest Iceland quantify significant variation in seasonal
temperature over the period from ∼360 B:C: to ∼A:D: 1660.
Twenty-six aragonitic bivalve specimens were selected to represent
intervals of climatic interest by using core sedimentological characteristics.
Carbonate powder was sequentially micromilled from
shell surfaces concordant with growth banding and analyzed for
stable oxygen (δ18O) and carbon (δ13C) isotope values. Because
δ18O values record subseasonal temperature variation over the lifetime
of the bivalves, these data provide the first 2,000-year secular
record of North Atlantic seasonality from ca. 360 cal yr B.C. to cal yr
A.D. 1660. Notable cold periods (360 B.C. to 240 B.C.; A.D. 410; and
A.D. 1380 to 1420) and warm periods (230 B.C. to A.D. 140 and A.D.
640 to 760) are resolved in terms of contrast between summer
and winter temperatures and seasonal temperature variability.
Literature from the Viking Age (ca. 790 to 1070) during the establishment
of Norse colonies (and later) in Iceland and Greenland
permits comparisons between the δ18O temperature record and
historical records, thereby demonstrating the impact of seasonal
climatic extremes on the establishment, development, and, in some
cases, collapse of societies in the North Atlantic.

]]> http://climateresearchnews.com/2010/03/clamshells-trump-tree-rings-as-a-temperature-proxy/feed/ 0 http://climateresearchnews.com/2010/03/ships-stuck-in-worst-baltic-sea-ice-for-15-years/ http://climateresearchnews.com/2010/03/ships-stuck-in-worst-baltic-sea-ice-for-15-years/#comments Tue, 09 Mar 2010 08:30:27 +0000 paul http://climateresearchnews.com/?p=2133 Thousands of passengers reportedly are stuck along with the ships ferrying them in Baltic Sea ice between Stockholm and the Aland Islands, located between Sweden and Finland. Both countries have sent icebreakers to rescue the ships in what is being called the worst Baltic freeze in 15 years.

Four ferries of the Viking Line, which routinely carries passengers between Sweden and Finland, are among the ships stuck in the ice, according to Swedish maritime authorities. Cargo vessels also have been affected, with up to 50 ships reportedly trapped.

4th March 2010, Examiner.com: Baltic Sea ice strands thousands of ferry passengers

Previous studies have largely overestimated mass loss from Alaskan glaciers over the past 40-plus years, according to Erik Schiefer, a Northern Arizona University geographer who coauthored a paper in the February issue of Nature Geoscience that recalculates glacier melt in Alaska.

The research team, led by Étienne Berthier of the Laboratory for Space Studies in Geophysics and Oceanography at the Université de Toulouse in France, says that glacier melt in Alaska between 1962 and 2006 contributed about one-third less to sea-level rise than previously estimated.

Science Daily: Mass Loss from Alaskan Glaciers Overestimated? Previous Melt Contributed a Third Less to Sea-Level Rise Than Estimated

February 18, 2010

PASADENA, Calif. – In 2007, the Arctic lost a massive amount of thick, multiyear sea ice, contributing to that year’s record-low extent of Arctic sea ice. A new NASA-led study has found that the record loss that year was due in part to the absence of “ice arches,” naturally-forming, curved ice structures that span the openings between two land points. These arches block sea ice from being pushed by winds or currents through narrow passages and out of the Arctic basin.

Beginning each fall, sea ice spreads across the surface of the Arctic Ocean until it becomes confined by surrounding continents. Only a few passages — including the Fram Strait and Nares Strait — allow sea ice to escape.

“There are a couple of ways to lose Arctic ice: when it flows out and when it melts,” said lead study researcher Ron Kwok of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “We are trying to quantify how much we’re losing by outflow versus melt.”

Kwok and colleagues found that ice arches were missing in 2007 from the Nares Strait, a relatively narrow 30- to 40-kilometer-wide (19- to 25-mile-wide) passage west of Greenland. Without the arches, ice exited freely from the Arctic. The Fram Strait, east of Greenland, is about 400 kilometers (249 miles) wide and is the passage through which most sea ice usually exits the Arctic.

Despite Nares’ narrow width, the team reports that in 2007, ice loss through Nares equaled more than 10 percent of the amount emptied on average each year through the wider Fram Strait.

“Until recently, we didn’t think the small straits were important for ice loss,” Kwok said. The findings were published this month in Geophysical Research Letters.

“One of our most important goals is developing predictive models of Arctic sea ice cover,” said Tom Wagner, cryosphere program manager at NASA Headquarters in Washington. “Such models are important not only to understanding changes in the Arctic, but also changes in global and North American climate. Figuring out how ice is lost through the Fram and Nares straits is critical to developing those models.”

To find out more about the ice motion in Nares Strait, the scientists examined a 13-year record of high-resolution radar images from the Canadian RADARSAT and European Envisat satellites. They found that 2007 was a unique year – the only one on record when arches failed to form, allowing ice to flow unobstructed through winter and spring.

The arches usually form at southern and northern points within Nares Strait when big blocks of sea ice try to flow through the strait’s restricted confines, become stuck and are compressed by other ice. This grinds the flow of sea ice to a halt.

“We don’t completely understand the conditions conducive to the formation of these arches,” Kwok said. “We do know that they are temperature-dependent because they only form in winter. So there’s concern that if climate warms, the arches could stop forming.”

To quantify the impact of ice arches on Arctic Ocean ice cover, the team tracked ice motion evident in the 13-year span of satellite radar images. They calculated the area of ice passing through an imaginary line, or “gate,” at the entrance to Nares Strait. Then they incorporated ice thickness data from NASA’s ICESat to estimate the volume lost through Nares.

They found that in 2007, Nares Strait drained the Arctic Ocean of 88,060 square kilometers (34,000 square miles) of sea ice, or a volume of 60 cubic miles. The amount was more than twice the average amount lost through Nares each year between 1997 and 2009.

The ice lost through Nares Strait was some of the thickest and oldest in the Arctic Ocean.

“If indeed these arches are less likely to form in the future, we have to account for the annual ice loss through this narrow passage. Potentially, this could lead to an even more rapid decline in the summer ice extent of the Arctic Ocean,” Kwok said.

For more information about NASA and agency programs, visit: http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Large sea ice outflow into the Nares Strait in 2007

R. Kwok

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA

L. Toudal Pedersen

Danish Meteorological Institute, Copenhagen, Denmark

P. Gudmandsen

Danish National Space Center, Technical University of Denmark, Lynby, Denmark

S. S. Pang

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA

Sea ice flux through the Nares Strait is most active during the fall and early winter, ceases in mid- to late-winter after the formation of ice arches along the strait, and re-commences after breakup in summer. In 2007, ice arches failed to form. This resulted in the highest outflow of Arctic sea ice in the 13-year record between 1997 and 2009. The 2007 area and volume outflows of 87 × 103 km2 and 254 km3 are more than twice their 13-year means. This contributes to the recent loss of the thick, multiyear Arctic sea ice and represents ∼10% of our estimates of the mean ice export at Fram Strait. Clearly, the ice arches control Arctic sea ice outflow. The duration of unobstructed flow explains more than 84% of the variance in the annual area flux. In our record, seasonal stoppages are always associated with the formation of an arch near the same location in the southern Kane Basin. Additionally, close to half the time another ice arch forms just north of Robeson Channel prior to the formation of the Kane Basin arch. Here, we examine the ice export with satellite-derived thickness data and the timing of the formation of these ice arches.

Received 20 November 2009; accepted 11 January 2010; published 9 February 2010.

Citation: Kwok, R., L. Toudal Pedersen, P. Gudmandsen, and S. S. Pang (2010), Large sea ice outflow into the Nares Strait in 2007, Geophys. Res. Lett., 37, L03502, doi:10.1029/2009GL041872.

In his speech, Mr Gore told the conference: “These figures are fresh. Some of the models suggest to Dr [Wieslav] Maslowski that there is a 75 per cent chance that the entire north polar ice cap, during the summer months, could be completely ice-free within five to seven years.”

However, the climatologist whose work Mr Gore was relying upon dropped the former Vice-President in the water with an icy blast.

“It’s unclear to me how this figure was arrived at,” Dr Maslowski said. “I would never try to estimate likelihood at anything as exact as this.”

The Times: ‘Inconvenient truth for Al Gore as his North Pole sums don’t add up’

UPDATE: There seems to be some confusion over this story, as reported here.

See also the 29th October 2009 CRN post: ‘Place Your Bets for a Sea Ice-Free Arctic’