Research: Antarctic Summer Melt Highest in 1,000 Years

This graphic says it all:

Abram et al.‘s Figure 5| Melt response over the past millennium. a, Schematic of Prince Gustav ice shelf history showing its presence (blue), intervals of rapid retreat (1957 and 1989; yellow) and collapse (1995; red). b,c, JRI mean temperature anomaly (green;b) and melt percentage (red;c) shown as 11-year moving averages. Thick lines are 21-year Gaussian kernel filters; dashed lines denote 1981–2000 mean. Lowest temperatures and melt occurred at AD 1410–1460, followed by progressive warming and a nonlinear melt increase. d, The occurrence of melt layers (grey lines) and a 100-year stepped average of melt frequency (purple) at Siple Dome in West Antarctica.

New research published in Nature Geoscience from Nerilie J. Abram et al. (subs. req’d) presents evidence that West  Antarctic ice melt accelerated over the course of the last 1,000 years.  About 400 years ago, average temperature anomalies (based off the 1981-2000 mean) increased from -1°C to -0.75°C (green curve in above graphic).  You can see the interannual and interdecadal variability in this time period, which was natural.  Then, starting 100 years ago, temperature anomalies rose from -0.75°C to today’s slightly positive anomaly.  As a result, the melt percentage jumped to 5% at James Ross Island.  That melt jump was nonlinear due to the ~0C melt threshold.  As the authors state, “where summer temperatures do exceed the melting threshold, the amount of melt produced is proportional to the sum of the daily positive temperatures rather than their mean.  This means that as average summer temperature increases and positive temperature days become warmer and more frequent, the amount of melt produced will exhibit an exponential increase”.

That cause-and-effect relationship is one reason why a 3°C average temperature rise carries so much more impact than a 2°C average temperature rise in polar regions.  It also explains why small changes in historical temperatures allowed the ice shelves to form in the first place.  The large “permanent” ice shelf collapses in recent history are the effect of rising temperatures.  It should be obvious too that predicting the timing of future ice shelf collapses is difficult if not impossible.

The Wilkins Ice Shelf collapsed suddenly in 2009.  This shelf is located southwest of the James Ross Island site cited above.  As I wrote in the Wilkins post, six other shelves completely collapsed in contemporary times: Prince Gustav Channel, Larsen Inlet, Larsen A, Larsen B, Wordie, Muller and the Jones Ice Shelf.  These ice shelves responded to the West Antarctic Ice Sheet (WAIS) warming observed in the last century or so.  WAIS warming is occurring faster than almost any other location on the globe.  There are areas in the Arctic and now the Antarctic that have observed +2.4°C warming from 1958 through 2009.  In addition to anthropogenic near-surface temperature rise, the ocean surrounding Antarctica has warmed recently.  Ice shelves are therefore being melted from above as well as below.  Does the following sound familiar?  “Over the past 18 years, Martinson and his colleagues have measured the physical properties of the ocean around Antarctica and came to the startling conclusion that the majority of the heat anomalies they have measured have occurred since 1960.  Unfortunately, those anomalies have been growing exponentially ever since.”

Additional coverage of this paper can be found here and here. [h/t Martin Lack for the HuffPo link]

Based on the above, we know that West Antarctica is warming very rapidly.  We know that warming anomalies are growing exponentially.  Problematically, even small temperature changes cause exponential changes in melt.  Exponential change growing off of exponential change creates a highly nonlinear, and therefore very unpredictable system.  What might that mean for the WAIS?  It could mean that rapid effects take place in the future.  In other words, ice sheet properties could change quickly.  Large melt areas could start one day without very little prior signal.  Additional ice sheet collapses could take place without much notice.  Increasing greenhouse gas emissions will cause increasing radiative forcing, which in turn will cause increased heat storage by some climate component (primarily the ocean to date, but also the atmosphere).  Current global energy imbalance guarantees decades’ worth of additional heating.  That heat will eventually impact Antarctica and its massive ice sheet.  Melting of global land-based ice to date increased global sea level by an average of 8 inches in the last 100 years.  If the entire West Antarctic Ice Sheet melted (which would happen sooner than East Antarctica because it rests on bedrock below sea level), sea levels would rise 4.8 meters.  The entire WAIS won’t melt for centuries, but sea levels would easily rise more quickly than the current 3mm/yr as annual WAIS melt increases due to increasing temperatures.

There is no catastrophe knocking on the door today, but WAIS melt will affect coastal regions this century.  Total sea level rise off the east coast of the US exceeded the global average, which has already caused communities to re-examine infrastructure.  Higher levees and other protective structures either have been built or are being considered by cities such as Washington, D.C., Norfolk, and New York City.  Efforts to date haven’t been sufficient (see Hurricane Sandy damage along the New Jersey shore), which points to a need for more aggressive analysis of needs and implementation of new climate-based policies.  Costs to these and other communities will grow as international mitigation efforts stall.

Research: West Antarctic Warming Greater Than Thought

A new article in Nature Geoscience, Central West Antarctica among the most rapidly warming regions on Earth (subs. req’d), presents up-to-date information on conditions of the West Antarctic Ice Sheet (WAIS).  The most common theme of climate science is present within this story: warming is occurring faster than scientists thought it was or projected just a few short years ago.  This study compares its results against similar efforts and confirms some of the fears of the cryosphere.  Large portions of both the Arctic and Antarctic are among the spots warming the fastest on Earth.  What does this mean?  It means accelerating sea level rise, influxes of fresh water into the world’s oceans, and rapidly changing ecosystems.  It means there are likely other effects of anthropogenic global warming occurring across the globe, but because our observation networks are sparse, we’re just not aware of them yet.

Two important figures from the paper:

Figure 1. Color shadings show the correlation between the annual mean temperatures at Byrd and the annual mean temperatures at every other grid point in Antarctica, computed using ERA-Interim 2-meter temperature time series from 1979 to 2011. The star symbol denotes the location of Byrd Station. The black circles denote the locations of permanent research stations with long-term temperature records.

The warming observed at Byrd Station is, by incorporating ERA-Interim reanalysis data, also exists across a significant portion of West Antarctica.  This development’s significance is this: the WAIS rests on bedrock and is grounded below sea level.  As the WAIS melts, the meltwater runs to the ocean from the land, raising sea levels.  If sea level around Antarctica rises high enough, the bottom of the WAIS will be exposed to water, which will hasten its melt.

Figure 2. Annual mean surface temperature change (trend×number of years) during 1958–2009 from the Byrd record (red and black circle) and from the CRUTEM4 data set (rest of map).

Figure 2 puts the Byrd warming into global context.  There are areas in the Arctic and now the Antarctic that have observed +2.4°C warming from 1958 through 2009.  The long time period is representative for climate and the non-zero warming represents change.  On a localized scale (WAIS), the warming observed at Byrd and likely at nearby locations probably counteracted the cooling resulting from increased circumpolar westerlies.  Those westerlies, as I’ve written about in my State of the Poles posts, were themselves the result of cooling in the Antarctic stratosphere as ozone depletion occurred.  In essence, the strong winds blowing across lines of longitude near Antarctica largely prevented warm air at higher latitudes from being blown across the continent.  The Byrd warming therefore presents an interesting case where this phenomenon isn’t the only one that occurs.

As the Montreal Protocol continues to reduce the amount of ozone-depleting substances in the stratosphere and the ozone layer replenishes itself, the anomalous westerlies will likely subside.  As additional warm air is advected over Antarctica, the continent will experience fuller effects of global warming.  In turn, the rest of the planet will experience the results of those effects.  This is an example of one science policy working while another science policy remains mostly flatlined.  The 2012 18th Conference of Parties continued to demonstrate that the same framework that allowed for the Montreal Protocol to be negotiated and successfully implemented has not and will not allow for a climate protocol.  Decades have passed while negotiators have tried time and again to do the same thing over and over.  A new approach is required.  Local, bottom-up efforts need to be expanded and stoked.  Someone somewhere has a much more effective set of solutions.  Heck, a bunch of someones somewheres have solution sets.  They need to be incubated and allowed to develop.  We need to take control of those strategies and processes.

New Satellite Data: East Antarctica Also Losing Mass

If the results of the study I’m discussing are robust, and not just true, many more climate change effects will become apparent sooner than many think.  It has been known for a number of years that the West Antarctic Ice Sheet (WAIS) has, on net, lost ice mass since ~2005.  This phenomenon has occurred concurrently with the Greenland ice sheet also losing mass over a similar time period.  That mass loss has contributed to a, until now, relatively small amount of sea level rise.

A new study suggests that sea level rise scenarios may need serious revision quickly: the East Antarctic Ice Sheet (EAIS) has, according to NASA’s GRACE satellite data, also lost mass in the 2005-present time period.  Why is this a potential big deal?  Because east Antarctica contains enough water to raise sea levels by 50-60m (160-200 feet!) if they melted completely.  In contrast, the water in the WAIS and Greenland amount to “only” 6-7m (~20 feet) each if they melted completely.  So the EAIS contains an order of magnitude more water than the other two large ice sheets on Earth.

Climate Change News – 5/22/09: Sea Level Rise Estimates, Oil & Military, Emissions in a Recession

Here are some of the climate-related news stories that I’ve seen this week:

A new study proposes that if the West Antarctic ice sheets melted, global sea level rise would only be 10 feet, not 20 as previously estimated by other studies.  The new study’s author claims that enough of the ice sheet would remain grounded on the Antarctic continent so that only some of the melting ice would find its way directly to the world’s oceans.  If true, this would be at least some good news in the sea level rise arena. One take-away message is that we still don’t know nearly enough about ice sheet and glacier dynamics to reliably forecast their future conditions.  These are interesting results – since they challenge previous findings, they need to be explored further.

Though not my chief concern over fossil fuel usage, a group of retired military officers argue in a recently released report that energy security and efforts to reduce the risks of climate change should be included in the nation’s national security and military planning.  From the article:

The concerns extend beyond America’s dependence on foreign oil, the report says, because no matter what the source, America’s dependence on oil “undermines economic stability, which is critical to national security.”

Also, the report called for modernizing the nation’s electric power system. The country’s “fragile domestic electricity grid makes our domestic military installations and their critical infrastructure unnecessarily vulnerable to incident, whether deliberate or accidental,” said the report.

The report raised alarm about three converging concerns: A future global oil market shaped by limited supplies and increasing demand, rising fossil fuel prices caused by regulating climate-changing emissions, and the impacts of climate change on global insecurity.

Another casualty of the 2008-09 recession?  CO2 emissions.  Many people were curious how the worst recession since the Great Depression would impact emission trends. Energy-related carbon dioxide emissions declined by 2.8 percent last year compared to 2007.  The Energy Information Administration attributed the decline to a 2.2 percent drop in energy consumption, largely because of high gasoline and diesel prices last summer and the sharp economic decline in the last half of the year.  It’s not the way anybody wanted emissions to be reduced – millions of Americans are unemployed and our economy is in tatters.  Meanwhile, Cons and ConservaDems watered the Waxman-Markey cap-and-trade legislation down significantly, as I’ll cover later.

Climate Change Effects Come Further Into Focus

As the science over the cause of climate change has become increasingly solidified, many researchers are expanding their examination of the effects of climate change.  Among other examples, some recent items of note include:

North American bird species are wintering further north. An Audubon Society study conclusively shows that hundreds of species of birds are spending winters further north in recent winters than they did 40 years ago.  Climate change has affected northern latitudes more than the mid-latitudes and tropics: they’ve grown warmer faster than any other region.  Migratory birds’ wintering patterns have been shifted.

Sea-Level Fingerprint of West Antarctic Collapse.  An important study that came out in last Friday’s issue of Science looks more closely at how sea levels around the world would be impacted if the West Antarctic Ice Sheet (WAIS) collapsed.  Contrary to the incomplete assessment that was part of the 2007 IPCC Report, sea level rise won’t be equitable across the globe.  Due to gravitational effects and uplift as ice mass disappears from land surfaces, oceans bordering North America and in the Indian Ocean could rise ~30% higher than previously assumed.  For instance, the IPCC forecasted a 5m sea level rise for areas near Washington, D.C.  The new assessment indicates a sea level rise of  6.3m (1.3m more) due to additional effects.

Okay, I’m going to bring up a couple of short-comings of this study, one of which the authors identified.  This assessment did not take into account the Greenland, East Antarctic or mountain ice sheets.  Anything that causes the collapse of the WAIS will undoubtedly also cause collapses elsewhere across the globe.  Thus, that 6.3m sea level rise for Washington, D.C. could easily go much, much higher.  The authors acknowledge that serious concerns about the impact on coastal communities is increased as a result of this study, not decreased.  Second, the authors compare their assessment to the IPCC’s.  As I’ve written before, recent observations from across the planet indicate that every model used in the 2007 IPCC Report underestimated recent climate change.  The poles are warming faster than any model used indicated.  Climate zones are shifting faster.  Drought areas are expanding further.  Birds’ wintering areas are shifting north sooner.  CO2 concentrations are higher and positive feedback mechanisms have been initiated.  This doesn’t mean the results of this Science paper are invalid, only that the specific sea level rise number used for contrast is already out of date.  Policy makers must be made aware of the most recent valid research, like this paper.  The challenge facing researchers is being able to provide robust, comprehensive assessments so that strong policies can be created.

Weeds will appear in new areas and disappear in others.  Land managers could have a short period of time to reintroduce native plants in areas that have been taken over by invasive species.  The biggest question is where will precipitation fall most often.

Hurricanes’ roles in influencing Northern Hemispheric winters are being explored.  The view that hurricanes are important in maintaining the balances the atmosphere works toward in much the same fashion as mid-latitude cyclones (think of the low pressure systems that typically move west to east) has gained traction in recent years.  This article describes another effort at working to determine how that mechanism compares to mechanisms like El Nino.