Support the Arctic Sea Ice Forum and Blog

Author Topic: West Antarctic Divide Core  (Read 4376 times)

sidd

  • Young ice
  • Posts: 4686
    • View Profile
  • Liked: 174
  • Likes Given: 0
West Antarctic Divide Core
« on: May 25, 2013, 08:30:33 AM »
Severinghaus at Byrd Polar Research



1 hour fourteen minute
worth the time.

sudd

AbruptSLR

  • Multi-year ice
  • Posts: 17161
    • View Profile
  • Liked: 330
  • Likes Given: 209
Re: West Antarctic Divide Core
« Reply #1 on: May 26, 2013, 01:06:08 AM »
Sidd,

Thanks for the great post, I very much enjoyed the video; especially the discussion about methane in the Southern Hemisphere/Antarctica.

Just to reinforce the point that there is more snowfall in the WAIS, than in the EAIS; which makes the layers in the WAIS ice core easier to read; I provide the attached image of current snowfall rates in Antarctica.

Best,
ASLR
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 17161
    • View Profile
  • Liked: 330
  • Likes Given: 209
Re: West Antarctic Divide Core
« Reply #2 on: May 26, 2013, 01:26:50 AM »
For those interest in one candidate for the 18K volcanic event mentioned in the video, I thought that I would post the following quote and attached image from the following website:

http://www.geog.cam.ac.uk/research/projects/erebusimpacts/

"Volcanological and atmospheric science at Mt. Erebus volcano (Antarctica)
Mt. Erebus is one of the largest active volcanoes on Earth. It reaches nearly 4 km above sea level, and is renowned in volcanological circles for its persistently active lava lake, which is sited in the summit crater. Despite its remote location, an extensive monitoring programme is in place, led by Philip Kyle at New Mexico Tech. The Cambridge Volcanology Group has participated in annual field campaigns on Erebus since 2003, making detailed measurements of heat, gas and aerosol emissions from the volcano using a variety of open path spectroscopy and in situ sampling techniques.
One of our findings is that Erebus is a significant source of nitrogen dioxide (NO2), a gas which plays an important role in tropospheric ozone chemistry. NO2 is not a primary volcanic gas but is probably formed by thermal fixation of atmospheric nitrogen at the hot surface of the lava lake. We have suggested that Erebus is the main point source for NO2 (and very likely other reactive nitrogen oxides) in the Antarctic troposphere. Given the high altitude and sustained degassing from the volcano, the measured emissions have implications for understanding aspects of both the atmospheric and cryospheric nitrogen chemistry of the continent.
We have also applied infrared spectroscopy to high time resolution measurements of emissions from the lava lake. Analysis of these data provides rich information on the dynamics and geometry of the plumbing system of the volcano. In a new paper, part of an in press Special Issue of Journal of Volcanology and Geothermal Research edited by Clive Oppenheimer and Philip Kyle, we have argued that the bulk of the gas emitted is sourced two kilometres below the lava lake yet is in chemical equilibrium with magma at the surface. We also find clear evidence that only part of the deep magma that yields carbon dioxide rises to shallower levels in the volcano's plumbing system."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • Young ice
  • Posts: 4686
    • View Profile
  • Liked: 174
  • Likes Given: 0
Re: West Antarctic Divide Core
« Reply #3 on: May 26, 2013, 01:31:45 AM »
Great results. Annually resolved to 62Kyr is amazing. Look what Lonnie Thompson had to go thru to get annually resolved to 1.6KYr in S. America. I'll believe it took tens of millions US$ and decades.

Illuminates the bipolar seesaw question, shows that Antarctica sees effects from the other end of the earth. The dating agreement with Chinese speleotherms is impressive. Detail in transitions like Bolling-Allerod and Younger Dryas is remarkable.

And I had no idea that Erebus was a halogen volcano.  Will definitely have to watch the thing again.

I think the gnome in front was the magnificent Lonnie Thompson, and the voice of the lady in the background might have been Ellen Mosely-Thompson.  Byrd Polar Research is a great place, check it out.

http://bprc.osu.edu/

sidd

AbruptSLR

  • Multi-year ice
  • Posts: 17161
    • View Profile
  • Liked: 330
  • Likes Given: 209
Re: West Antarctic Divide Core
« Reply #4 on: May 26, 2013, 07:39:19 PM »
Sidd,

The Byrd Polar Research contains a lot of good data, and in keeping with the title of this thread, please see the following abstract relevent to the WAIS Divide Ice Core, from the Nineteenth Annual WAIS Workshop, 2012:

"High Basal Melt at the WAIS--‐Divide ice--‐core siteT.J. Fudge, Gary Clow, Howard Conway, Kurt Cuffey, Michelle Koutnik, Tom Neumann, Kendrick Taylor, and Ed Waddington

We use the depth-age relationship and borehole temperature profile from the WAIS-Divide ice core site to determine the basal melt rate and corresponding geothermal flux. The drilling of the WAIS-Divide ice core has been completed to 3400 m depth, about 60 m above the bed. The age of the deepest ice is 62 ka, younger than anticipated, with relatively thick annual layers of ~1 cm.  The borehole temperature profile shows a large temperature gradient in the deep ice. We infer a basal melt rate of 1.5 (±0.5) cm yr-1 using a 1-D ice flow model constrained by these data sets. The melt rate implies a geothermal flux of ~230 mW m-2, three times the measured value of 70 mW m-2 at Siple Dome.

We compile radio-echo sounding data sets to assess the spatial extent of high melt. Deep internal layers are the most useful for inferring spatial patterns of basal melt. Unfortunately, the IceBridge WAIS-core flight and two site-selection surveys did not image consistent reflectors deeper than Old Faithful (2420 m and 17.8 ka). A ground-based survey by CReSIS (Laird et al., 2010) was able to image consistent layers as deep as 3000 m, but the survey is not oriented along the ice-flow direction making interpretation more difficult. There is no obvious draw down of deep internal layers that would indicate an area of localized melt. While this suggests a uniform melt rate within the survey, it might also indicate that other factors (e.g. accumulation gradients, rough bed topography) obscure the influence of basal melt on the internal layer depths."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 17161
    • View Profile
  • Liked: 330
  • Likes Given: 209
Re: West Antarctic Divide Core
« Reply #5 on: May 28, 2013, 02:59:07 AM »
The following from the Eighteenth Annual WAIS Workshop (2011), indicates how volcanically active the WAIS is now (Behrendt recommends that its potential contribution not be ignored when assessing the risks of coming SLR), and has been in the recent past:

"Geophysical evidence of Ice-Magma interactions beneath the West Antarctic Ice Sheet in the West Antarctic Rift System
John C. Behrendt
INSTAAR University of Colorado, Boulder
And USGS, Denver
Radar Ice Sounding and Aeromagnetic Surveys reported over the West Antarctic Ice Sheet WAIS have been interpreted as evidence of subglacial eruptions. Several active volcanoes have shown evidence of eruption through the WAIS and several other active volcanoes are present beneath the WAIS (e.g. Corr et al., 2009; Blankenship et al., 1993) reported from radar ice sounding and aeromagnetic data (Behrendt et al., 1995; 2004). Aeromagnetic profiles (>10,000 km) acquired in the early 1960s over the West Antarctic Ice Sheet (WAIS) combined with coincident aeromagnetic and radar ice sounding in 1978-79 indicated numerous high-amplitude, shallow-source, magnetic anomalies over a very extensive area of the volcanically active West Antarctic rift system interpreted as caused by subglacial volcanic rocks. These early aerogeophysical surveys defined this area as >500,000 km2. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys since 1990 provide three dimensional characterization of the magnetic field and bed topography beneath the ice sheet. These 5-50-km width, semicircular magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice have been interpreted as evidence of subglacial eruptions. Behrendt et al, (2005, 2008) interpreted these anomalies as indicating >1000 "volcanic centers." requiring high remanent normal (and at least 10% reversed) magnetizations in the present field direction. These data have shown that >80% of the anomaly sources at the bed of the WAIS, have been modified by the moving ice into which they were injected, requiring a younger age than the WAIS (about 25 Ma). Although exposed volcanoes surrounding the WAIS extend in age to ~34 m.y., Mt Erebus, (<1 Ma) Mt. Melbourne, (<0.26 Ma), and Mt. Takahae (<0.1 Ma) are examples of exposed active volcanoes in the WAIS area. However, the great volume of volcanic centers is buried beneath the WAIS. If only a very small percentage of these >1000 volcanic, magnetic-anomaly sources are active today, or in the recent past, in the drainage area of the WAIS, subglacial volcanism may still have a significant effect on the dynamics of the WAIS. Interpreted active subglacial volcanism is revealed by aerogeophysical data reported by Blankenship et al., (1993, Mt. Casertz), and Corr and Vaughan, (2008, near Hudson Mts.), who raised the question of possible volcanic effects on the regime of the WAIS. Wingham et al. (2009) reported an average rate of volume loss from 2.6 to 10.1 km3 /yr from 1995 to 2006 for the Pine Island Glacier in the vicinity of the active subglacial volcano near the Hudson Mts. Probably wet-based areas of the WAIS would be the most likely to be impacted. Here I discuss these geophysical data over the WAIS, and conclude that even if there is a very low probability, future effects on the stability of the WAIS and associated sea-level rise should not be ignored, as changes observed in the past 20 years resulting from global warming, could be accelerated by subglacial volcanism."

The attached figures are also from a Behrendt 2011 pptx.

« Last Edit: May 28, 2013, 03:04:41 AM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 17161
    • View Profile
  • Liked: 330
  • Likes Given: 209
Re: West Antarctic Divide Core
« Reply #6 on: May 28, 2013, 04:17:09 PM »
As Icebgone seemed to be questioning the accuracy of the WAIS Divide borehole over in the "Paleo" thread; I thought that I would post the following information and weblinks providing information about how the procedures used to verify this information:

The following summary is from the following website:
http://waisdivide.unh.edu/

"Innovations in Ice Drilling Enable Abrupt Climate Change Discoveries
A revolutionary drilling system leads to the retrieval of additional ice for evidence of abrupt climate change from the Antarctic Ice Sheet.

Deep within ice sheets in the polar regions is an archive of evidence about the climate of the past. Ice cores drilled in the past have yielded amazing scientific discoveries, for example that climate can change abruptly in less than ten years, and that the CO2 in the atmosphere now is higher than evidenced from the last 800,000 years. At the WAIS Divide site, a cold area of the West Antarctic Ice Sheet where the abundant snowfall rarely melts, the ice contains many tens of thousands of years of annual information about past climate. At specific depths in the ice sheet, including from times of abrupt climate change in the past, scientists are investigating past greenhouse gas records and other evidence from the ice that will help to understand why and how abrupt changes occur.
Now, for the first time, significant innovations in drilling engineering are providing scientists with replicate ice cores from targeted depths and directions in the ice sheet. The newly developed, state-of-the-art Replicate Coring System is capable of retrieving additional ice cores from specific depths on the uphill side of the main borehole. Engineering that addresses priority science needs for ice coring and drilling is provided by the National Science Foundation (NSF) through a collaborative arrangement through the Ice Drilling Program Office (IDPO) led by Dartmouth, in collaboration with the University of New Hampshire and the Ice Drilling Design and Operations (IDDO) group at the University of Wisconsin. The Replicate Coring technique, developed and tested by the IDDO engineers as part of the DISC Drill, is now producing the first-ever replicate ice cores from a nearly vertical main ice borehole. The Wisconsin group started the design of the DISC Drill in 2002 in response to the desire of the US science community for a deep coring drill that would incorporate the ability to retrieve additional cores from deviations from the main borehole. The DISC Drill was put into service at WAIS Divide during the 2007-08 Antarctic field season and completed the main borehole during 2011-12 reaching a depth of 3,405 meters. Testing of the Replicate Coring System began at the end of the 2011-12 season.
Jay Johnson, the Lead Drilling Engineer for the endeavor says "There was a bit of uncertainty after we drilled the first replicate core whether we had actually recovered it in the core barrel. After waiting a half hour for the drill to return to the surface from 3002.6m, the drill team and core handlers assembled in the drill arch were dead silent as we watched the drill tower tilt and waited for the first glimpse into the drill head. A loud cheer erupted at the sight of the core! It was a surreal moment for the drill team and especially for the IDDO engineers, Nicolai Mortensen, Chris Gibson, and myself, who developed the technology and hardware for the world's first robotic ice coring drill. This is truly an engineering marvel and a new chapter in ice core drilling that will lead to new scientific discoveries."
"A stupendous accomplishment! The IDDO engineers have succeeded at a feat that presented many difficulties, all of which they have overcome by dedication, ingenuity, skill, and just plain hard work. They have broken new ground in the ice coring business with the first directed deviation from a main borehole with a suspended electromechanical drill. This opens a new door for the future of ice core drilling. Our heartiest congratulations go to the whole IDDO crew at WAIS Divide." says Charlie Bentley, the P.I. of IDDO.
"The realization of replicate coring at WAIS Divide has been the result of a lot of ingenuity and hard work by the staff of IDDO. The success of effort to retrieve replicate cores was far from certain and was only possible because of the interest and confidence in the project and IDDO shown by Julie Palais the NSF Program Manager, and Chief Scientist for the WAIS Divide project Kendrick Taylor, Lead Scientist for Replicate Coring Jeff Severinghaus, and numerous other scientists interested in ice cores", said Don Lebar, IDDO Program Director.
"The Replicate Coring success is the result of a long journey in engineering development, working toward the attainment of very aggressive and sometimes seemingly impossible goals", says Alex Shturmakov, DISC/Replicate Coring Project Manager of IDDO.
"This is a great accomplishment! It is clear that all of the hard work on everyone's part has paid off." says Dr. Julie Palais, Program Manager at NSF.
This engineering achievement, which was funded by NSF investments in a new paradigm for ice core drilling through the IDPO-IDDO enterprise (EOS Trans AGU, 91(39), 345-346, 2010) is important for the scientific discoveries that are critical to the future of all people. NSF manages the U.S. Antarctic Program through which it coordinates all U.S. scientific research on the southernmost continent and aboard ships in the Southern Ocean as well as related logistics support."

For more information on the replicate coring system, please see:

http://www.icedrill.org/equipment/development.shtml#replicate

“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 17161
    • View Profile
  • Liked: 330
  • Likes Given: 209
Re: West Antarctic Divide Core
« Reply #7 on: June 22, 2013, 02:10:35 AM »
http://projects.noc.ac.uk/andrex/results
The following quote from a longer article from "The Antarctic Sun" (see link below), discusses how "replicate" cores were obtained by reentering the "WAIS Divide Core" hole at levels that showed abrupt climate change that occurred in the past on timescales of decades.  As such information is analyzed it will provide additional support for the risks that we are now facing w.r.t. ASLR:

http://antarcticsun.usap.gov/science/contenthandler.cfm?id=2858

"The eighth and final season of drilling operations in 2012-13 involved using a newly developed drill capable of reentering the original borehole and collecting more ice at specific depths of scientific interest. Specifically, this “replicate” core was drilled at locations where researchers have previously identified abrupt climate changes, when global temperature shifted on a timescale of decades."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • Multi-year ice
  • Posts: 17161
    • View Profile
  • Liked: 330
  • Likes Given: 209
Re: West Antarctic Divide Core
« Reply #8 on: June 04, 2014, 11:58:57 PM »
The following linked reference provides new findings from the WAIS Divide and the EDML ice cores, Antarctica, and indicates that the atmospheric methane record in Antarctica is much different than that for Greenland, indicating a local source of methane:

Winstrup, M., Vinther, B.M., Sigl, M., McConnell, J., Svensson, A.M. and Wegner, A. (2014)
Development and comparison of layer-counted chronologies from the WAIS Divide and EDML ice cores, Antarctica, over the last glacial transition (10-15 ka BP)
EGU General Assembly 2014, held 27 April - 02 May 2014 in Vienna, Austria, id. EGU2014-12193-1

http://waisdivide.unh.edu/Publications/DisplayArticle.shtml?REF_ID=1365

Abstract: "Some ice cores can be very precisely dated far back in time by counting the annual layering in various impurity records, and the most robust chronologies rely on the parallel analysis of annual features expressed in multiple data sets. Layer-counted Antarctic ice-core chronologies are now emerging: Multi-parameter layer counting has been carried out for the Holocene and late glacial section of the EDML ice core, Dronning Maud Land (Vinther et al., in prep.), and a layer-counted timescale for the WAIS Divide core, West Antarctica, reaching back to 30 kyr BP, was recently completed (WDC06A-7; WAIS Divide Members, 2013). Beyond 24 kyr b2k, the main part of this timescale relies solely on electrical measurements on the core.
We here use a novel statistical framework for automated annual layer counting (Winstrup et al., 2012) to extend and improve the two chronologies from EDML and WAIS Divide. Using this method, we have 1) revised the multi-parameter layer counts for the EDML ice core back to 15 kyr BP, and 2) employed high-resolution chemistry measurements from WAIS Divide to obtain a layer-counted multi-parameter timescale for WAIS Divide over the same period (10-15 ka b2k). The EDML and WAIS Divide ice cores have been tightly synchronized using volcanic marker horizons, thus allowing a detailed comparison of annual layer counts between tie points using the various approaches. The corresponding timescales are compared also to the EDML timescale from the flow-model based AICC2012 chronology (Veres, 2012).
For the Holocene section of the period (10-11.7 ka BP), all timescales show very good agreement. The peculiar accumulation anomaly observed in the WAIS Divide layer thicknesses in the beginning of the Holocene is confirmed by the multi-parameter layer counts from both WAIS Divide and EDML. The transition into the Holocene has generally proven a difficult period to date by annual layer counting, since the appearance of an annual layer in the various records can change. This is reflected in discrepancies between the currently available timescales: Using the new volcanic synchronization between EDML and WAIS Divide, we find that the AICC2012 is diverging very significantly from the WDC06A-7 timescale over this period (~100 yr between 12-13 kyr b2k). Similarly, methane matching shows significant discrepancies between WDC06A-7 and the Greenland Ice Core Chronology 2005 (GICC05), which cannot be reconciled within the specified uncertainty of the respective annual layer counts (WAIS Divide Members, 2013). The two new timescales developed here provide another piece of information to this puzzle."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson