Support the Arctic Sea Ice Forum and Blog

Author Topic: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe  (Read 99253 times)

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #100 on: May 30, 2014, 02:08:43 AM »
The following abstract comes from the International Glacial Society Proceeding 65 at the following link:

http://www.igsoc.org/symposia/2014/chamonix/proceedings/procsfiles/procabstracts_65.htm

Candy et al 2014 discuss progress made towards an adaptive resolution multiscale model of the PIIS ocean cavity:

70A1106
Towards an adaptive resolution multiscale model of Pine Island Glacier ice-shelf ocean cavity
Adam CANDY, Paul HOLLAND, Adrian JENKINS, Matthew PIGGOTT
Corresponding author: Adam Candy
Corresponding author e-mail: adam.candy@imperial.ac.uk

Abstract: "Recent observational studies have helped to constrain estimates of the melt behaviour underneath Pine Island Glacier (PIG). Generally, however, observations are limited due to the relatively inaccessible and inhospitable environment. A solid ice cover, up to many kilometres thick, bars access to the water column, so that observational data can only be obtained by inference from above, drilling holes through, or launching autonomous vehicles beneath, the ice. This is further exacerbated by the fact that results of these recent studies have implied a significant proportion of the melting (~80%) occurs in networks of sub-kilometre-scale basal channels close to the grounding line, some of the most inaccessible parts of sub-ice-shelf ocean cavities. Accurately representing these small-scale processes in conventional ocean models is a huge challenge even in focused regional studies, and will not be possible in global coupled climate simulations in the near future. We present the development of a new model of PIG that is capable of resolving the range of scales necessary to evaluate the melt distribution and forming processes that dominate. This is built on the fluidity model that simulates non-hydrostatic dynamics on meshes that, like the model of Timmermann and others (2012), can be unstructured. In this case, the grid can be unstructured in all three dimensions and use an anisotropic adaptive-in-time resolution to optimize the mesh and calculation in response to evolving solution dynamics. The parameterization of melting in this model has been validated in idealized cavity domains and a validation is underway for the dynamic treatment of the ice–ocean interface. The model is not limited to a vertical coordinate system, which enables it to accurately represent ice fronts, and small shallow features. We will discuss the development of this model of PIG; including the cavity domain, conforming to appropriately filtered boundaries generated from data collected during the BAS Autosub 2009 expedition, and the simulation of non-hydrostatic dynamics to date. This model has the potential to capture the high spatial variation seen in melt rates in the small-scale channels, and as a result provide valuable insights into the physical processes driving the observed large melting and modulation of ice–ocean interactions at kilometre scales."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #101 on: July 13, 2014, 05:48:05 PM »
The linked reference discusses icequake seismicity associated with a propagating ice shelf rift, which typically occurs during a major calving event from an ice shelf (in this case the Amery Ice Shelf).  Such research should contribute to a better understanding of the risks of major ice shelf calving events, which if their frequency were to accelerate could contribute to the collapse of the ice shelf itself (note the Jakobshavn Glacier's Ice Shelf has already collapsed, and similar collapses could occur for the Thwaites Eastern Ice Shelf and the Pine Island Ice Shelf, within the next few of decades; which would greatly accelerate ice mass loss from the ASE basin):

Heeszel, D. S., H. A. Fricker, J. N. Bassis, S. O'Neel, and F. Walter (2014), Seismicity within a propagating ice shelf rift: The relationship between icequake locations and ice shelf structure, J. Geophys. Res. Earth Surf., 119, 731–744, doi:10.1002/2013JF002849.

http://onlinelibrary.wiley.com/doi/10.1002/2013JF002849/abstract

Abstract: "Iceberg calving is a dominant mass loss mechanism for Antarctic ice shelves, second only to basal melting. An important process involved in calving is the initiation and propagation of through-penetrating fractures called rifts; however, the mechanisms controlling rift propagation remain poorly understood. To investigate the mechanics of ice shelf rifting, we analyzed seismicity associated with a propagating rift tip on the Amery Ice Shelf, using data collected during the austral summers of 2004–2007. We apply a suite of passive seismological techniques including icequake locations, back projection, and moment tensor inversion. We confirm previous results that show ice shelf rifting is characterized by periods of relative quiescence punctuated by swarms of intense seismicity of 1 to 3 h. Even during periods of quiescence, we find significant deformation around the rift tip. Moment tensors, calculated for a subset of the largest icequakes (Mw > −2.0) located near the rift tip, show steeply dipping fault planes, horizontal or shallowly plunging stress orientations, and often have a significant volumetric component. They also reveal that much of the observed seismicity is limited to the upper 50 m of the ice shelf. This suggests a complex system of deformation that involves the propagating rift, the region behind the rift tip, and a system of rift-transverse crevasses. Small-scale variations in the mechanical structure of the ice shelf, especially rift-transverse crevasses and accreted marine ice, play an important role in modulating the rate and location of seismicity associated with the propagating ice shelf rifts."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #102 on: September 13, 2014, 01:03:30 AM »
The linked reference has an open access pdf, and provides guidance on the recent mass balance for the Pine Island, and Thwaites; glaciers:

Medley, B., Joughin, I., Smith, B. E., Das, S. B., Steig, E. J., Conway, H., Gogineni, S., Lewis, C., Criscitiello, A. S., McConnell, J. R., van den Broeke, M. R., Lenaerts, J. T. M., Bromwich, D. H., Nicolas, J. P., and Leuschen, C., (2014), "Constraining the recent mass balance of Pine Island and Thwaites glaciers, West Antarctica, with airborne observations of snow accumulation", The Cryosphere, 8, 1375-1392, doi:10.5194/tc-8-1375-2014.

http://www.the-cryosphere.net/8/1375/2014/tc-8-1375-2014.html

Abstract: "In Antarctica, uncertainties in mass input and output translate directly into uncertainty in glacier mass balance and thus in sea level impact. While remotely sensed observations of ice velocity and thickness over the major outlet glaciers have improved our understanding of ice loss to the ocean, snow accumulation over the vast Antarctic interior remains largely unmeasured. Here, we show that an airborne radar system, combined with ice-core glaciochemical analysis, provide the means necessary to measure the accumulation rate at the catchment-scale along the Amundsen Sea coast of West Antarctica. We used along-track radar-derived accumulation to generate a 1985–2009 average accumulation grid that resolves moderate- to large-scale features (>25 km) over the Pine Island–Thwaites glacier drainage system. Comparisons with estimates from atmospheric models and gridded climatologies generally show our results as having less accumulation in the lower-elevation coastal zone but greater accumulation in the interior. Ice discharge, measured over discrete time intervals between 1994 and 2012, combined with our catchment-wide accumulation rates provide an 18-year mass balance history for the sector. While Thwaites Glacier lost the most ice in the mid-1990s, Pine Island Glacier's losses increased substantially by 2006, overtaking Thwaites as the largest regional contributor to sea-level rise. The trend of increasing discharge for both glaciers, however, appears to have leveled off since 2008."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • ASIF Upper Class
  • Posts: 1502
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #103 on: September 20, 2014, 08:19:52 PM »
Since I have previously whined about the paucity of full Stokes analyses, i should point out Wilkens(2014)

www.the-cryosphere-discuss.net/8/4913/2014/tcd-8-4913-2014.pdf

In particular Fig.6 and 7

Temperate beds under PIG, as suspected, but detail is nice.

sidd

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #104 on: September 20, 2014, 10:02:47 PM »
sidd,

Thanks for the reference and the pointers to Fig. 6 & 7; however, the points that I find most interesting are about what the authors call Tributary 13 (& MacGregor et al call the SW Tributary) in that: : (a) the first attached image shows clearly that Tributary 13 is located directly on the basin divide with the Thwaites Basin; and (b) the second attached image shows that the ice velocities in the Tributary 13 are as fast as any ice in PIG, and as soon as the PIIS calving face retreats upstream sufficiently then these velocities will accelerate serving to destabilize Thwaites.

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

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #105 on: September 24, 2014, 11:40:05 PM »
The linked reference (with an open access pdf) makes conservative estimates of the sensitivity of PIG dynamics (groundling line retreat, ice velocities etc.) to climate forcing for the next fifty years.  Significantly, the attached image shows the results of one such conservative projection indicating that the grounding line for the SW Tributary is primed for early retreat; which could serve to trigger an early destabilization of the Thwaites Glacier.

Seroussi, H., Morlighem, M., Rignot, E., Mouginot, J., Larour, E., Schodlok, M., and Khazendar, A., (2014), "Sensitivity of the dynamics of Pine Island Glacier, West Antarctica, to climate forcing for the next 50 years", The Cryosphere, 8, 1699-1710, doi:10.5194/tc-8-1699-2014.

http://www.the-cryosphere.net/8/1699/2014/tc-8-1699-2014.pdf

Abstract: "Pine Island Glacier, a major contributor to sea level rise in West Antarctica, has been undergoing significant changes over the last few decades. Here, we employ a three-dimensional, higher-order model to simulate its evolution over the next 50 yr in response to changes in its surface mass balance, the position of its calving front and ocean-induced ice shelf melting. Simulations show that the largest climatic impact on ice dynamics is the rate of ice shelf melting, which rapidly affects the glacier speed over several hundreds of kilometers upstream of the grounding line. Our simulations show that the speedup observed in the 1990s and 2000s is consistent with an increase in sub-ice-shelf melting. According to our modeling results, even if the grounding line stabilizes for a few decades, we find that the glacier reaction can continue for several decades longer. Furthermore, Pine Island Glacier will continue to change rapidly over the coming decades and remain a major contributor to sea level rise, even if ocean-induced melting is reduced."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • ASIF Upper Class
  • Posts: 1502
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #106 on: September 30, 2014, 04:07:19 AM »
They said it couldn't be done.

"GOCE was designed to determine the Earth’s mean gravity field [Visser et al., 2002], and it was not anticipated that it could observe temporal gravity field variations."

"While Moore and King [2010] predicted that GOCE cannot detect an Antarctic ice change, ... "

But it seems it can ... when combined with GRACE ...

Results: For the period Nov 2009-July 2012
PIG -55+/-9 GT/yr,
Thwaites/Haines/Smith/Kohler -63+/-12 GT/y,
Metz -67+/-7 GT/y

Pretty,pretty work. Bouman(2014) doi:10.1002/2014GL060637

Compare say with Helm(2014) Cryostat result for WAIS for Jan2012-2013 of -188+/11 GT/yr
doi:10.5194/tcd-8-1673-2014

sidd

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #107 on: September 30, 2014, 05:38:43 AM »
sidd,

Thank you for a great post about GOCE's triumph.  The following two links have the same beautiful video showing the extreme precision of the measurement of the annual changing in ice mass in the ASE marine glaciers from 2009 to 2012:

http://grist.org/article/antarctic-ice-melt-causes-small-shift-in-gravity/

http://www.esa.int/Our_Activities/Observing_the_Earth/GOCE/GOCE_reveals_gravity_dip_from_ice_loss

Best,
ASLR
« Last Edit: September 30, 2014, 03:52:17 PM by AbruptSLR »
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • ASIF Upper Class
  • Posts: 1502
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #108 on: September 30, 2014, 06:56:38 AM »
A surprise is Getz, mass loss was estimated to be around a third of the result from this paper.

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #109 on: September 30, 2014, 04:38:39 PM »
sidd,

Yes Getz is the surprise as every article before this that I had since implied that the ice mass loss from Getz was from the floating ice shelf; however, the high precision of the GOCE (as indicated by the attached image taken from the ESA video) confirms that Getz has also made a serious contribution to SLR from Nov 2009 to June 2012.

However, I would like to say that during this time period we experienced a very strong La Nina event, which reduced the advection of warm CDW into the ASE; which in my opinion explains why the SLR contribution from the Thwaites Glacier was relatively low (it has twice the mass of the PIG).  Therefore, I am concerned that as we have ended a period of positive PDO/IPO it seems likely that the SLR contribution from all of the ASE marine glaciers will likely accelerate over the next 20 to 30 years (ie until the 2040-2060 Timeframe).

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

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #110 on: September 30, 2014, 06:05:53 PM »
Given the importance of the Bouman et al (2014), I provide the following link and abstract:

Bouman, J., M. Fuchs, E. Ivins, W. van der Wal, E. Schrama, P. Visser, and M. Horwath (2014), Antarctic outlet glacier mass change resolved at basin scale from satellite gravity gradiometry, Geophys. Res. Lett., 41, 5919–5926, doi:10.1002/2014GL060637.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060637/abstract

Abstract: "The orbit and instrumental measurement of the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite mission offer the highest ever resolution capabilities for mapping Earth's gravity field from space. However, past analysis predicted that GOCE would not detect changes in ice sheet mass. Here we demonstrate that GOCE gravity gradiometry observations can be combined with Gravity Recovery and Climate Experiment (GRACE) gravity data to estimate mass changes in the Amundsen Sea Sector. This refined resolution allows land ice changes within the Pine Island Glacier (PIG), Thwaites Glacier, and Getz Ice Shelf drainage systems to be measured at respectively −67 ± 7, −63 ± 12, and −55 ± 9 Gt/yr over the GOCE observing period of November 2009 to June 2012. This is the most accurate pure satellite gravimetry measurement to date of current mass loss from PIG, known as the “weak underbelly” of West Antarctica because of its retrograde bed slope and high potential for raising future sea level."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • ASIF Upper Class
  • Posts: 1502
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #111 on: October 01, 2014, 09:57:25 PM »
Just as I was admiring Bouman(2014)  here comes Velicogna(2014)
doi:10.1002/2014GL061052 which is at least as good.

Using GRACE data alone (!) it is possible to tease out regional variation.
I suspected this was possible, but they haveactually done it (!) using
a masscon approach. Very nice. They then couple with RACM02 for SMB.
I must say that RACM02 seems to be turning into the goto tool for this
sorta thing.

Now to the results:

1)"Overall, in Greenland, SMB has contributed 68% of the GRACE-derived
mass loss (-180±33 Gt/yr versus a total loss of -265±59 Gt/yr) and 79%
of the observed acceleration (23.3±4.7 Gt/yr2 versus a total acceleration of
29.7±1.3 Gt/yr2 ) during 2003-2012."

Agrees with Enderlin(2014) doi:10.1002/2013GL059010 in that SMB dominates
linear term, but they have shown it dominates quadrature (acceleration)
term as well. Interesting that they see little regional acceleration
in NEGIS, contrary to Khan(2014) doi:10.1038/nclimate2161

2)Amundsen sea sector they get -116+/-6GT/yr for the period 2003-2013 agrees
with Bouman(2014) within error for the time period in Bouman. Acceleration is

significant at 12.7+/- 1.6 GT/yr

3)those are  hefty accelerations. If the curves were really exponentials
instead of parabolae that would mean a doubling time of 7 yr. But i dont
think the data can differentiate between order 2 and exponential yet.
It will become clearer in a few decades.

What have i done to deserve _two_ such nice papers within a few days ?
I must have been very good lately.

sidd

Lennart van der Linde

  • ASIF Middle Class
  • Posts: 697
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #112 on: October 01, 2014, 10:49:31 PM »
Thank you, sidd, for keeping us up-to-date with these scary numbers. Are there any looming negative feedbacks in sight?

A 7-yr doubling time roughly resembles the doubling time of the Chinese economy over the past decade. But that would be a coincidence...

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #113 on: October 01, 2014, 10:57:35 PM »
As a public service, I provide the following reference information for the Velicogna et al paper that sidd cited in Reply #111:

I. Velicogna, T. C. Sutterley and M. R. van den Broeke, (2014), "Regional acceleration in ice mass loss from Greenland and Antarctica using GRACE time-variable gravity data," Geophysical Research Letters, DOI: 10.1002/2014GL06105

http://onlinelibrary.wiley.com/doi/10.1002/2014GL061052/abstract

Abstract: "We use GRACE monthly gravity fields to determine the regional acceleration in ice mass loss in Greenland and Antarctica for 2003–2013. We find that the total mass loss is controlled by only a few regions. In Greenland, the southeast and northwest generate 70% of the loss (280∓58 Gt/yr) mostly from ice dynamics, the southwest accounts for 54% of the total acceleration in loss (25.4∓1.2 Gt/yr2) from a decrease in surface mass balance (SMB), followed by the northwest (34%), and we find no significant acceleration in the northeast. In Antarctica, the Amundsen Sea (AS) sector and the Peninsula account for 64% and 17%, respectively, of the total loss (180∓10 Gt/yr) mainly from ice dynamics. The AS sector contributes most of the acceleration in loss (11∓4 Gt/yr2) and Queen Maud Land, East Antarctica is the only sector with a significant mass gain due to a local increase in SMB (63∓5 Gt/yr)."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #114 on: October 01, 2014, 11:03:17 PM »
For those who would like to learn more about the Regional Atmospheric Climate MOdel (RACMO2), I provide the following link:

http://www.staff.science.uu.nl/~lenae101/pubs/Lenaerts2013aSOM.pdf
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Lennart van der Linde

  • ASIF Middle Class
  • Posts: 697
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #115 on: October 01, 2014, 11:44:37 PM »
Skeptical Science also gives a short update of some recent papers, including some mentioned above:
http://skepticalscience.com/Antarctica-Greenland-Losing-Ice.html

Totten Glacier is also of concern.

sidd

  • ASIF Upper Class
  • Posts: 1502
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #116 on: October 02, 2014, 01:21:16 AM »
Re:feedbacks

Everything is deeply intertwingled.

1)I think we have activated the Weertmann instability in WAIS, and collapse is now inevitable. All we have left to discuss is the timeframe.
2)A feedback that was thought possible was a warming ocean dropping more snow on Antarctica. But as we see from Velicogna(2014) and others it seems  only to have operated very sporadically in Dronning Maud Land. And there is a a paper i believe that shows that increased snowfall can actually increase ice efflux but i do not immediately recall the reference.
3)The increase in Southern Ocean winter sea ice is another wicked synergy. Naively i thought that Antarctic ice flow ended at the coastline. Not so it seems. Consider: Ocean heat melts basal ice, fresh water efflux then exits, spreads north and refreezes where it is exposed to seasonally warmer water much more efficiently than when it was in the base of an ice shelf. In other words, the ocean is not only sucking ice outta the interior of WAIS by eroding the base and speeding flow, it is then transporting the ice as meltwater north, refreezing it in a region where it can melt it at leisure, reclaiming latent heat in the process. So the ocean is sucking ice much further north than the coastline. And observe the clever way it cycles the heat: it donates heat to the meltwater at the ice shelf base, and reclaims it further north as the meltwater freezes in winter.
4)In the case of Greenland, I fear that precipitation there will be increasingly rain as opposed to snow. I believe there is a paper by Tedesco or Fettweis or somebody that shows this happening over the next century. Again this is something that i did not understand, how could ocean heat get into Greenland except at the tongues of maritime glaciers.

In short, the ocean is very large, very clever, and wants in your basement.

sidd

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #117 on: October 02, 2014, 01:55:37 AM »
sidd & Lennart,

Don't forget that the Velicogna et al (2014) paper only considers ice mass loss during the El Nino hiatus period, during which time the advection of warm CDW into the ASE is reduced.  Now that we are entering a positive PDO/IPO phase advection of CDW into the ASE should accelerate for the next 20 to 35 years; which should further acceleration ice mass loss from the WAIS.

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

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #118 on: October 02, 2014, 07:28:43 PM »
To provide some visual support for my position that advection of CDW into the ASE has (and is likely to continue) increased since the 2000-2013 timeframe, I attach the accompanying Terra image of the Pine Island Bay area showing extensive loss of sea ice in this area even though sea ice extent in Antarctica in general is near an all time high.  This local loss of sea ice in Pine Island Bay is clearly related to advection of CDW and is atypical of the 2000-2013 period.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #119 on: October 03, 2014, 01:03:50 AM »
Further to my last post, the attached NSIDC image of Antarctic sea ice anomalies for Sept 2014 shows that not only is the sea ice in Pine Island Bay melting anomalously early, but also the outer perimeter of the sea ice offshore of the ASE is also anomalously low for this time of year.  This supports the idea that land-based ice mass loss in the ASE is likely anomalously high due to higher than normal ocean water advection.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #120 on: October 03, 2014, 11:45:18 PM »
The attached image was taken from the Modis Oct 3 2014 mosaic for Antarctica and focuses on the Amundsen Sea area and shows how extensive the exceptionally early break-up of the sea ice throughout this region is occurring.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

johnm33

  • ASIF Middle Class
  • Posts: 758
    • View Profile

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #122 on: October 09, 2014, 08:14:06 PM »
The first attached image if taken from the Modis Antarctic mosaic for Oct 9 2014, and shows how extremely fractured the sea ice is both the ASE and the Bellingshausen Sea.  The second attached image shows the earth surface wind map for Oct 9 2014, showing that the local winds in this area are currently blowing from land to offshore; and if this wind pattern continues from some days, a meaningful fraction of this local fractured sea ice could be blown out to more northerly latitudes where it would likely melt.  If this happens (now or soon), it would expose both the ASE, and the Bellingshausen Sea, coastlines to increase storm wave exposure that could promote glacial ice calving from the local ice shelves.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #123 on: October 14, 2014, 01:20:31 AM »
The linked reference provides more evidence that the BSB is providing geothermal basal heat to accelerate the destabilization of the Thwaites Glacier:

Theresa M. Damiani, Tom A. Jordan, Fausto Ferraccioli, Duncan A. Young, and Donald D. Blankenship, (2014), "Variable crustal thickness beneath Thwaites Glacier revealed from airborne gravimetry, possible implications for geothermal heat flux in West Antarctica", Earth and Planetary Science Letters Volume 407, 1, Pages 109–122, DOI: 10.1016/j.epsl.2014.09.023

http://www.sciencedirect.com/science/article/pii/S0012821X14005780

Abstract: "Thwaites Glacier has one of the largest glacial catchments in West Antarctica. The future stability of Thwaites Glacier's catchment is of great concern, as this part of the West Antarctic Ice Sheet has recently been hypothesized to already be en route towards collapse. Although an oceanic trigger is thought to be responsible for current change at the grounding line of Thwaites Glacier, in order to determine the effects of this coastal change further in the interior of the West Antarctic Ice Sheet it is essential to also better constrain basal conditions that control the dynamics of fast glacial flow within the catchment itself. One major contributor to fast glacial flow is the presence of subglacial water, the production of which is a result of both glaciological shear heating and geothermal heat flux. The primary goal of our study is to investigate the crustal thickness beneath Thwaites Glacier, which is an important contributor to regional-scale geothermal heat flux patterns. Crustal structure is an indicator of past tectonic events and hence provides a geophysical proxy for the thermal status of the crust and mantle. Terrain-corrected Bouguer gravity disturbances are used here to estimate depths to the Moho and mid-crustal boundary. The thin continental crust we reveal beneath Thwaites Glacier supports the hypothesis that the West Antarctic Rift System underlies the region and is expressed topographically as the Byrd Subglacial Basin. This rifted crust is of similar thickness to that calculated from airborne gravity data beneath neighboring Pine Island Glacier, and is more extended than crust in the adjacent Siple Coast sector of the Ross Sea Embayment. A zone of thinner crust is also identified near the area's subaerial volcanoes lending support to a recent interpretation predicting that this part of Marie Byrd Land is a major volcanic dome, likely within the West Antarctic Rift System itself. Near-zero Bouguer gravity disturbances for the subglacial highlands and subaerial volcanoes indicate the absence of supporting crustal roots, suggesting either (1) thermal support from a warm lithosphere or alternatively, and arguably less likely; (2) flexural support of the topography by a cool and rigid lithosphere, or (3) Pratt-like compensation. Although forward modeling of gravity data is non-unique in respect to these alternative possibilities, we prefer the hypothesis that Marie Byrd Land volcanoes are thermally-supported by warmer upper mantle. The presence of such inferred warm upper mantle also suggests regionally elevated geothermal heat flux in this sector of the West Antarctic Rift System and consequently the potential for enhanced meltwater production beneath parts of Thwaites Glacier itself. Our new crustal thickness estimates and geothermal heat flux inferences in the Thwaites Glacier region are significant both for studies of the structure of the broader West Antarctic Rift System and for assessments of geological influences on West Antarctic Ice Sheet dynamics and glacial isostatic adjustment models."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #124 on: October 14, 2014, 08:33:02 PM »
The linked reference (with a free pdf) presents numerical model studies relating the oceanographic and geometric (of the cavity beneath the PIIS) controls on ice melting for the PIG (and PIIS).  They found that after an initial surge of ice melting after the 1970's with grounding line retreated past the well-known subglacial ridge; thereafter the melting rate was more dominated by the depth of the thermocline.  I remind readers that the depth of the thermocline has been related to the ENSO cycle (via the ASL) and that as we enter a period of increasingly positive PDO the depth of the thermocline should be increasingly conducive to accelerated rates of ice melting for at least the next 20 to 25 years.

J. De Rydt, P.R. Holland, P. Dutrieux, and A. Jenkins, (2014), "Geometric and oceanographic controls on melting beneath Pine Island Glacier", Journal of Geophysical Research-Oceans, 119:2420-2438. doi: 10.1002/2013JC009513

http://www.antarctica.ac.uk/met/ph/docs/2014_DeRydt&Al_JGRO.pdf

Abstract: "Observations beneath the floating section of Pine Island Glacier have revealed the presence of a subglacial ridge which rises up to 300 m above the surrounding bathymetry. This topographic feature probably served as a steady grounding line position until sometime before the 1970s, when an ongoing phase of rapid grounding line retreat was initiated. As a result, a large ocean cavity has formed behind the ridge, strongly controlling the ocean circulation beneath the ice shelf and modulating the ocean water properties that cause ice melting in the vicinity of the grounding line. In order to understand how melt rates have changed during the various phases of cavity formation, we use a high-resolution ocean model to simulate the cavity circulation for a series of synthetic geometries. We show that the height of the ridge and the gap between the ridge and ice shelf strongly control the inflow of warm bottom waters into the cavity, and hence the melt rates. Model results suggest a rapid geometrically controlled increase of meltwater production at the onset of ice thinning, but a weak sensitivity to geometry once the gap between the ridge and ice shelf has passed a threshold value of about 200 m. This provides evidence for a new, coupled, ice-ocean feedback acting to enhance the initial retreat of an ice stream from a bedrock high. The present gap is over 200 m, and our results suggest that observed variability in melt rates is now controlled by other factors, such as the depth of the thermocline."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #125 on: November 10, 2014, 03:05:30 AM »
While I have cited the following Rignot et al 2014 reference previously; here I attached an image from this reference that shows that ice flux (from 1974 to 2013) across the 2011 Thwaites Glacier grounding line is currently accelerating faster than any other Amundsen Sea Embayment marine glacier (which is a very disturbing trend):

Rignot, E., Mouginot, J., Morlighem, M., Seroussi, H. and Scheuchl, B., (2014), "Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011", Geophysical Research Letter, DOI: 10.1002/2014GL060140.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #126 on: January 29, 2015, 01:57:29 AM »
In order to give this important thread a bump, and to illustrate some of the consequences if the WAIS should start to collapse in this timeframe, I attach the two associated images from the linked pdf:

http://www.agci.org/dB/PPTs/05S1_RTol_0713.pdf
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • ASIF Upper Class
  • Posts: 1502
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #127 on: January 29, 2015, 05:48:41 AM »
That paper from agci.org is by Tol, whom i distrust. He also says that SLR rates of greater than 1m/century breaks the model ...

I will wait for a more reliable source and a better model.

sidd

Lennart van der Linde

  • ASIF Middle Class
  • Posts: 697
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #128 on: January 29, 2015, 07:55:40 AM »
I think the presentation by Tol above was based on the Atlantis Project by Tol et al 2006:
http://dspace.ubvu.vu.nl/bitstream/handle/1871/31946/191890.pdf?sequence=1

Neo-Atlantis by Olsthoorn et al 2005 gave input for this:
http://www.fnu.zmaw.de/fileadmin/fnu-files/publication/working-papers/waishollandwp.pdf

They published this as Olsthoorn et al 2008:
http://link.springer.com/article/10.1007%2Fs10584-008-9423-z

And then nothing much happend with this work, probably because the risk of such WAIS-collapsed was judged to be too small to worry about. Which should really change now.
« Last Edit: January 29, 2015, 08:09:15 AM by Lennart van der Linde »

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #129 on: January 29, 2015, 05:21:16 PM »
And then nothing much happend with this work, probably because the risk of such WAIS-collapsed was judged to be too small to worry about. Which should really change now.

My purpose in posting the Tol information was not to give support to his work, but as Lennart points out the question of the consequence of a possible early start for abrupt SLR, ASLR, should be re-evaluated now (especially in light of the Bassis et al and Pollard et al findings about cliff failures and hydrofracturing [which I sometimes call meltpond mechanism and/or the Thwaites effect]).  We need to remember that scientists are happy to update their SLR projections whenever they have sufficient data, so the fact that even a few months ago that they discounted the rapid collapse of marine glaciers is no guarantee at all to protect society from the serious consequences of an early start to ASLR (here assumed to have a threshold of 1m of SLR in three decades and then probably accelerating).

The Olsthoorn et al 2008 just assumes a start date for ASLR of 2030, which seems plausible to me if we take the Greenland marine terminating glaciers as starting to collapse in 2030, and then the WAIS marine glaciers joining them in collapse by 2040.  As Lennart has pointed out previously, it will take some time before SLR guidance agencies recognize this risk (say by AR6 [if it is generated] by 2021), then it will take time for decision makers, financiers and designers/planners to decide where/how to fight ASLR and where/how to retreat from ASLR (say by 2030).  As ASLR will be happening everywhere in the world simultaneously we can assume at least the following consequence:

1. Where we fight or retreat the costs of new constructions will likely double or triple due to the simultaneous demand on contractors.
2. Those who cannot retreat in an organized fashion will become refugees which will put high demands on governments, who will lack sufficient revenues to meet their other challenges of degraded coastal road, rail and port/harbor transportation, degrades water supplies due to salinity contamination which will also corrode buried utilities, and blocked sewer systems.  Such effects will also collapse tax revenues.
3.  Food production will degrade rapidly in all of the deltas of the world & delivery of food from the upstream river systems will be blocked by sedimentation of the river mouth (eg the Mississippi, Mekong, Nile, etc).
4.  Compromise of the ability of all militaries worldwide to project power overseas to address local hotspots (both military & humanitarian), as all naval bases and many airports will be compromised.
5.  High-tides and storm surge will be made worse by ASLR.

I could go on but you get the idea.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #130 on: January 30, 2015, 08:56:30 PM »
I thought that I would quickly note that I would not expect much of the cliff failure & hydrofracturing mechanisms postulated by Pollard et al 2015 in the PIG/Thwaites area prior to the 2040-2060 timeframe, and as Pfeffer et al 2008 does not include either of these two mechanisms, it is possible that the Pfeffer et al 2008 Beta PDF analysis by Lempert et al 2012, may provide some idea how likely ASLR is to begin by 2030.

Lempert, R., Sriver, R.L. and Keller, K., (2012); "Characterizing Uncertain Sea Level Rise Projections to Support Investment Decisions" Report to POLA.

The two attached associated images (that I have posted before) indicate that this probability may be on the order of about 15%
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #131 on: April 05, 2015, 09:47:06 PM »
The linked reference (the second link has a free pdf) ties the warming of the Tropical Atlantic SST to a strengthening of both the Antarctic Circumpolar Winds and the Amundsen Bellingshausen Sea Low (ABSL/ASL) via atmospheric Rossby waves in all seasons except the austral summer.  The conclusions of this paper (see the extract below) recommends that efforts be made to inter-relate this Atlantic tropical-Antarctic teleconnection with other tropical teleconnections (such as those identified by Fogt et al 2011, see the first attached image relating El Nino events & negative Southern Annular Mode, SAM, conditions that promote teleconnection of Tropical Pacific energy towards the Amundsen Sea Embayment, via atmospheric Rossby wave-trains).  As we are now likely approaching very strong El Nino conditions by October 2015, it will be very interesting to see whether both the Tropical Atlantic and the Tropical Pacific soon teleconnect large amounts of atmospheric energy into Western Antarctica.

Additionally, the second attached image today from the Earth nullschool shows that the ABSL is relatively strong (i.e. has a relatively low central pressure) and is currently directing energy directly into the Amundsen Sea Embayment, ASE.

XICHEN LI, EDWIN P. GERBER, DAVID M. HOLLAND, AND CHANGHYUN YOO, (2015), "A Rossby Wave Bridge from the Tropical Atlantic to West Antarctica", J. Climate, 28, 2256–2273, doi: http://dx.doi.org/10.1175/JCLI-D-14-00450.1


http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00450.1

http://polarmet.osu.edu/ACCIMA/li_gerber_jc_2015.pdf

Abstract: "Tropical Atlantic sea surface temperature changes have recently been linked to circulation anomalies around Antarctica during austral winter. Warming in the tropical Atlantic associated with the Atlantic multidecadal oscillation forces a positive response in the southern annular mode, strengthening the Amundsen–Bellingshausen Sea low in particular. In this study, observational and reanalysis datasets and a hierarchy of atmospheric models are used to assess the seasonality and dynamical mechanism of this teleconnection.  Both the reanalyses and models reveal a robust link between tropical Atlantic SSTs and the Amundsen–Bellingshausen Sea low in all seasons except austral summer. A Rossby wave mechanism is then shown to both explain the teleconnection and its seasonality. The mechanism involves both changes in the excitation of Rossby wave activity with season and the formation of a Rossby waveguide across the Pacific, which depends critically on the strength and extension of the subtropical jet over the west Pacific. Strong anticyclonic curvature on the poleward flank of the jet creates a reflecting surface, channeling quasi-stationary Rossby waves from the subtropical Atlantic to the Amundsen–Bellingshausen Sea region. In summer, however, the jet is weaker than in other seasons and no longer able to keep Rossby wave activity trapped in the Southern Hemisphere. The mechanism is supported by integrations with a comprehensive atmospheric model, initial-value calculations with a primitive equation model on the sphere, and Rossby wave ray tracing analysis."

Extract: "Antarctic climate is also influenced by other tropical–polar teleconnections (Fogt et al. 2011; Ding et al. 2012), and key questions remain concerning the relative importance of these effects. The time scales of tropical SST variability differs significantly from one region to another (e.g., ENSO and the east Pacific dominate on interannual time scales, while the AMO and Pacific decadal oscillation are more significant on longer time scales). Moreover, SSTs in different tropical ocean basins may interact with each other through tropical ocean interbasin teleconnections. It is thus important to further investigate the relative importance and the relationship between the teleconnections from different tropical ocean sectors as a function of time scale."

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

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #132 on: April 14, 2015, 07:39:20 PM »
For what it is worth, the attached Earth MSLP surface Wind Map for April 14 2015 shows that the ABSL is currently positioned so that the associated winds are currently driving warm CDW into the ASE (below the sea ice).
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #133 on: August 03, 2015, 05:52:37 PM »
As I am particularly concerned about the probability that the grounded iceberg at the tip of the residual Thwaites Ice Tongue may become free floating either this austral summer (2015-16) or next (2016-17); which raises the risk that the trapped field of free floating approximately 1km by 2km icebergs that compose the residual Ice Tongue will then free to float away.  If/when the floating portion of the residual Ice Tongue floats away, I am then concerned that cliff failure (and possibly future hydrofracturing due to future surface ice melting) will then occur in the grounded fractured ice in the trough at the base of the Ice Tongue (see the first attached image from January 2013 that shows the boundary between floating and grounded ice above the trough and illustrates how the ice flowing into the trough developed through crevasses that pre-divided this grounded ice into approximately 1km by 2km chucks that are highly susceptible to calving and floating away).

In this regard I provide the second attached figure of the Thwaites residual Ice Tongue on August 1, 2015 per the Sentinel 1a satellite (from the linked Polarview site); which shows: (a) the iceberg at the tip of the residual Ice Tongue has moved beyond the tip of the Thwaites Eastern Ice Shelf; and (b) some approximately 1km by 2km icebergs have already begun to float away as compared to the third attached image from Landsat 8 for March 6 2015.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #134 on: August 04, 2015, 10:04:37 PM »
The following paper finds that the disintegration of the Thwaites Ice Shelf (both the eastern ice shelf and the ice tongue) is accelerating due to basal melting and warm CDW intrusion beneath the eastern ice shelf since 2000), together with the shear stress between the eastern ice shelf and the residual ice tongue due to differential ice flow rates:

Kim et al (2015), "Disintegration and acceleration of Thwaites Ice Shelf on the Amundsen Sea revealed from remote sensing measurements", GIScience & Remote Sensing, Volume 52, Issue 4, DOI: 10.1080/15481603.2015.1041766

Abstract: "Thwaites Ice Shelf in the Amundsen Sea is one of the biggest ice shelves in West Antarctica and is well known for significant mass changes. In the shear zone between Thwaites Glacier Tongue and its eastern ice shelf, shear stress forced by different flow rates of the ice shelves is causing the ice to break apart. A time series analysis of remote sensing data obtained by Landsat 7 Enhanced Thematic Mapper Plus (ETM+), TerraSAR-X, and airborne synthetic aperture radar (SAR) revealed that the shear zone has extended since 2006 and eventually disintegrated in 2008. We quantified the acceleration of Thwaites Ice Shelf with time by using the feature tracking method. The buttressing loss induced by the extension of the shear zone and progressive disintegration accelerated the flow of Thwaites Glacier Tongue, which in turn increased the shear stress on its eastern ice shelf. We determine causes of disintegration in the newly formed shear zone to be oceanic basal melting and structural weakening induced by Circumpolar Deep Water intrusion beneath the eastern ice shelf since 2000. The structural weakening was examined by using the density distribution of rifts and crevasses on the ice shelf, which were well identified from high-resolution SAR and optical satellite images."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #135 on: August 04, 2015, 10:14:34 PM »
The linked article discusses the October 2012 IceBridge Antarctica mission to survey the Thwaites Ice Shelf area.  The first attached image of the ice self is from before the 2012 Thwaites Ice Tongue breakage event, the section image is from Tinto & Bell 2011:

http://blogs.ei.columbia.edu/2012/10/18/launching-the-season-with-a-key-mission-icebridge-antarctica-2012/
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #136 on: August 07, 2015, 04:40:26 PM »
The attached image of the Thwaites Eastern Ice Shelf, TEIS, is from Polarview (Sentinel 1a) for August 7 2015; and I want to draw attention to the somewhat recent calved iceberg from the southwest corner of the TEIS; which also be seen in the August 1 2015 image, but cannot be seen in the March 2015 images.  This provides support to the idea that not only is the Thwaites residual Ice Tongue degrading rapidly due to warm CDW advection, but so is the TEIS.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

solartim27

  • ASIF Citizen
  • Posts: 428
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #137 on: August 12, 2015, 06:37:21 PM »
Here is a view of the old Twaites shelf from 8/1 to 8/11.  I rotated it for maximum view.  It may not show up on this small scale, but all the cracks have expanded within the last 10 days.  It appears to me that disintegration will occur relatively soon.  2 second delay on gif.
FNORD

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #138 on: August 12, 2015, 10:13:46 PM »
Here is a view of the old Twaites shelf from 8/1 to 8/11.  I rotated it for maximum view.  It may not show up on this small scale, but all the cracks have expanded within the last 10 days.  It appears to me that disintegration will occur relatively soon.  2 second delay on gif.

solartim27,

I think that what you are showing broke-off from the Thwaites Ice Tongue in 2002 and has been grounded ever since (see the attached image from MacGregor et al 2012).

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

Gray-Wolf

  • ASIF Middle Class
  • Posts: 601
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #139 on: August 14, 2015, 05:42:01 PM »
Am I right in thinking we saw a  paper looking at how La Nina/ Nina like conditions slowed losses from PIG/Thwaites over the late noughties/early teens due to wind/current anoms?

If so are we about to see big losses over the coming Southern Summer?
KOYAANISQATSI

ko.yaa.nis.katsi (from the Hopi language), n. 1. crazy life. 2. life in turmoil. 3. life disintegrating. 4. life out of balance. 5. a state of life that calls for another way of living.
 
VIRESCIT VULNERE VIRTUS

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #140 on: August 15, 2015, 01:23:23 AM »
Am I right in thinking we saw a  paper looking at how La Nina/ Nina like conditions slowed losses from PIG/Thwaites over the late noughties/early teens due to wind/current anoms?

If so are we about to see big losses over the coming Southern Summer?

Gray-Wolf,

I believe that you are referring to the following article that I discussed (& provided images from) in Reply #245 in the "PIG has calved" thread.

Best,
ASLR

Pierre Dutrieux, Jan De Rydt, Adrian Jenkins, Paul R. Holland, Ho Kyung Ha, Sang Hoon Lee, Eric J. Steig, Qinghua Ding, E. Povl Abrahamsen, and Michael Schröder, 2014, "Strong Sensitivity of Pine Island Ice-Shelf Melting to Climatic Variability", Science; Published online 2 January 2014 DOI:10.1126/science.1244341

http://www.sciencemag.org/content/early/2014/01/02/science.1244341.abstract

http://www.sciencemag.org/content/suppl/2014/01/02/science.1244341.DC1/Dutrieux.SM.pdf

http://www.ccpo.odu.edu/~klinck/Reprints/PDF/dutrieuxScience14.pdf

Abstract:
"Pine Island Glacier has thinned and accelerated over recent decades, significantly contributing to global sea-level rise. Increased oceanic melting of its ice shelf is thought to have triggered those changes. Observations and numerical modeling reveal large fluctuations in the ocean heat available in the adjacent bay and enhanced sensitivity of ice shelf melting to water temperatures at intermediate depth, as a seabed ridge blocks the deepest and warmest waters from reaching the thickest ice. Oceanic melting decreased by 50% between January 2010 and 2012, with ocean conditions in 2012 partly attributable to atmospheric forcing associated with a strong La Niña event. Both atmospheric variability and local ice shelf and seabed geometry play fundamental roles in determining the response of the Antarctic Ice Sheet to climate."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #141 on: August 15, 2015, 11:56:52 PM »
The following link provides images and information about the March 2002 calving of Iceberg B-22 from the Thwaites Ice Tongue:

http://www.noaanews.noaa.gov/stories/s879.htm
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

solartim27

  • ASIF Citizen
  • Posts: 428
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #142 on: August 17, 2015, 02:23:11 AM »
I had mentioned a calving on Thwaites on the PIG thread last week.  Here is a closeup of the area for 8/1, 8/11, and 8/16.  No big change for the 16th, but one of the bergs splits and rolls.  The Sentinal shot misses the last PIG remnant stuck on the pinnacle, so no idea what is going on there.
FNORD

steve s

  • ASIF Lurker
  • Posts: 42
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #143 on: August 17, 2015, 07:04:23 PM »
ST, would you please estimate from the image pixels the distance the Thwaites calving face retreated during August? Since the retreat distance varies along the face, the maximum point of retreat would do.

I think of the maximum as a relatively easy qualitative measure of the release of stored strain, suitable for quick comparison with new nearby events. In the case of the Thwaites in the next few years, time series on retreat maximums and on the intervals between events may prove both interesting and useful.








« Last Edit: August 17, 2015, 07:48:27 PM by steve s »

solartim27

  • ASIF Citizen
  • Posts: 428
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #144 on: August 17, 2015, 07:50:26 PM »
ST, would you please estimate from the image pixels the distance the Thwaites calving face retreated during August? Since the retreat distance varies along the face, the maximum point of retreat would do.

I think of the maximum as relatively easy qualitative measure of the release of stored strain suitable for quick comparison with new events nearby. In the case of the Thwaites in the next few years, time series on retreat maximums and intervals between events will probably prove interesting -- and useful for pedagogy.
Sorry, thats beyond my capabilities, I'm just eyeballing a screen shot to matchup as best I can.  I don't think the front has retreated, might have advanced some, except for the bit that cracked off. 
FNORD

steve s

  • ASIF Lurker
  • Posts: 42
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #145 on: August 17, 2015, 10:54:59 PM »
I was looking at a spot of obvious retreat. I don't know the scale of the image or the area covered by a pixel to approximate the distance, but I do wonder.

Given the rather obvious increase in floating ice chunks, if the calving face did not retreat, the glacier must have surged. Big icequake; near the grounding line as I have read the various posts.

solartim27

  • ASIF Citizen
  • Posts: 428
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #146 on: August 18, 2015, 11:07:49 PM »
The article discussed in this link is previously posted under the Collapse Scenario thread by LvdL, but this link has a nice video of the glaciers retreating, though it covers 300 years.  I would not be surprised if it is faster than that.
http://www.climatecentral.org/news/west-antarctica-sea-level-estimates-19345
FNORD

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #147 on: August 25, 2015, 01:45:15 AM »
Here is a useful reference about changes in Amundsen sea ice from 1979 to 2014:

Stammerjohn SE, Maksym T, Massom RA, Lowry KE, Arrigo KR, et al. 2015. Seasonal sea ice changes in the Amundsen Sea, Antarctica, over the period of 1979–2014. Elem. Sci. Anth. 3: 000055 doi: 10.12952/journal.elementa.000055

https://www.elementascience.org/articles/55

https://www.elementascience.org/articles/55/tabs/figures_and_data


Abstract: "Recent attention has focused on accelerated glacial losses along the Amundsen Sea coast that result from changes in atmosphere and ocean circulation, with sea ice playing a mediating but not well-understood role. Here, we investigated how sea ice has changed in the Amundsen Sea over the period of 1979 to 2014, focusing on spatio-temporal changes in ice edge advance/retreat and percent sea ice cover in relation to changes in winds. In contrast to the widespread sea ice decreases to the east and increases to the west of the Amundsen Sea, sea ice changes in the Amundsen Sea were confined to three areas: (i) offshore of the shelf break, (ii) the southern Pine Island Polynya, and (iii) the eastern Amundsen Sea Polynya. Offshore, a 2-month decrease in ice season duration coincided with seasonal shifts in wind speed and direction from March to May (relating to later ice advance) and from September to August (relating to earlier retreat), consistent with reported changes in the depth/location of the Amundsen Sea Low. In contrast, sea ice decreases in the polynya areas corresponded to episodic or step changes in spring ice retreat (earlier by 12 months) and were coincident with changes to Thwaites Iceberg Tongue (located between the two polynyas) and increased southeasterly winds. Temporal correlations among these three areas were weak, indicating different local forcing and/or differential response to large-scale forcing. Although our analysis has shown that part of the variability can be explained by changes in winds or to the coastal icescape, an additional but unknown factor is how sea ice has responded to changes in ocean heat and freshwater inputs. Unraveling cause and effect, critical for predicting changes to this rapidly evolving ocean-ice shelf-sea ice system, will require in situ observations, along with improved remote sensing capabilities and ocean modeling."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

AbruptSLR

  • ASIF Emperor
  • Posts: 12964
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #148 on: September 15, 2015, 10:09:47 PM »
Some people may feel that it is cherry picking to point at a daily NOAA surface temp anom plot such as the attached for Sept 15 2015; however, I believe that the exceptionally warmth indicated for the WAIS is characteristic of the strengthening El Nino that is underway.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

Lennart van der Linde

  • ASIF Middle Class
  • Posts: 697
    • View Profile
Re: Hazard Analysis for PIG/Thwaites from 2012 to 2040-2060 Timeframe
« Reply #149 on: September 29, 2015, 08:24:31 PM »
Excellent article by Chris Mooney on the the risk of Thwaites collapse and the urgent need for more research on this key WAIS-glacier:
http://www.washingtonpost.com/news/energy-environment/wp/2015/09/29/scientists-declare-an-urgent-mission-study-west-antarctica-and-fast/