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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #150 on: January 29, 2014, 10:54:52 PM »
The following linked free access article presents the latest analysis of the GRACE satellite data from 2003 to 2012, and it clearly indicates that ice mass loss from the WAIS is accelerating with time:

Williams, Simon D.P.; Moore, Philip; King, Matt A.; Whitehouse, Pippa L.. 2014 Revisiting GRACE Antarctic ice mass trends and accelerations considering autocorrelation. Earth and Planetary Science Letters, 385. 12-21. 10.1016/j.epsl.2013.10.016

http://www.sciencedirect.com/science/article/pii/S0012821X13005797


Abstract

"Previous GRACE-derived ice mass trends and accelerations have almost entirely been based on an assumption that the residuals to a regression model (including also semi-annual, annual and tidal aliasing terms) are not serially correlated. We consider ice mass change time series for Antarctica and show that significant autocorrelation is, in fact, present. We examine power-law and autoregressive models and compare them to those that assume white (uncorrelated) noise. The data do not let us separate autoregressive and power-law models but both indicate that white noise uncertainties need to be scaled up by a factor of up to 4 for accelerations and 6 for linear rates, depending on length of observations and location. For the whole of Antarctica, East Antarctica and West Antarctica the scale factors are 1.5, 1.5 and 2.2 respectively for the trends and, for the accelerations, 1.5, 1.5 and 2.1. Substantially lower scale-factors are required for offshore time series, suggesting much of the time-correlation is related to continental mass changes. Despite the higher uncertainties, we find significant (2-sigma) accelerations over much of West Antarctica (overall increasing mass loss) and Dronning Maud Land (increasing mass gain) as well as a marginally significant acceleration for the ice sheet as a whole (increasing mass loss)."
« Last Edit: February 04, 2014, 11:08:24 PM by AbruptSLR »
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #151 on: February 06, 2014, 12:30:39 AM »
The accompanying SLR graph from the University of Colorado from Feb 5, 2014 shows that the recent dip in SLR has stopped before the end of 2013.
« Last Edit: February 13, 2014, 01:03:14 AM by AbruptSLR »
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #152 on: February 13, 2014, 12:59:04 AM »
I consider that AVISO (see link below and the accompanying data and image) to be one of the best indicators of measured SLR; and the latest data through November 2013 indicates that sea level was increasing in November 2013 at a rate of 3.26 mm/yr (which is higher than prior estimates, see also the University of Colorado estimate in my immediate prior post).  If an El Nino happens in 2014 – 2015, this rate of SLR will surely increase still faster.

http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/


2013.481617 6.567891e-02
2013.508764 6.640031e-02
2013.535912 6.669096e-02
2013.563059 6.618282e-02
2013.590207 6.515256e-02
2013.617354 6.426951e-02
2013.644502 6.399452e-02
2013.667946 6.439201e-02
2013.704944 6.429930e-02
2013.725944 6.483989e-02
2013.753092 6.517826e-02
2013.780240 6.570968e-02
2013.807387 6.635191e-02
2013.834535 6.697119e-02
2013.861682 6.754522e-02
2013.888830 6.809363e-02
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #153 on: February 13, 2014, 05:26:09 PM »
I would just like to note that English et al 2014 has clearly tied the increase in Pacific Trade Wind velocity to both the El Nino and Mean Global Temperature Anomaly hiatus's, and they also related variations in Pacific wind shear stress to the IPO (see the first image and see the "Forcing" thread for other discussion and references).  However, here I would like to note that from 2011 to 2012 (see: http://iod.ucsd.edu/~peter/pdfs/Bromirski_etal_Eos_2012.pdf ) Scripps published a series of reports and articles relating the Pacific wind behavior to sea level in the North Pacific.  The second attached image (from Scripps) shows the related SLR trend for the West Coast also from 1900 to 2010, and comparing these two images one sees that the US West Coast sea level is correlated to the Pacific wind behavior which is in turn related to the IPO and Mean Global Temperature Anomaly  (see English et al 2014).  Thus I suspect that with the projected El Nino (and beginning of a positive PDO index) in 2014-2015, this will reduce the Pacific Trade Wind velocity and will increase US West Coast rate of SLR after 2014 (at least until the IPO index changes). 

Finally, I thought that I would throw in a third image of the 1900 to 2011 PDO trend (which I think is interesting to compare to the IPO trend and the Mean Global Temperature Anomaly trend).
It is interesting to think about the implications of various oscillating ocean/atmospheric indexes (like the: PDO, IPO, ENSO etc) being superimposed upon a trend line of an accelerating Mean Global Temperature Anomaly.  Recent GCM projections forecast increasingly frequent large EL Nino events (see: Wenju Cai, Simon Borlace, Matthieu Lengaigne, Peter van Rensch, Mat Collins, Gabriel Vecchi, Axel Timmermann, Agus Santoso, Michael J. McPhaden, Lixin Wu, Matthew H. England, Guojian Wang, Eric Guilyardi & Fei-Fei Jin, (2014), "Increasing frequency of extreme El Niño events due to greenhouse warming", Nature Climate Change, doi:10.1038/nclimate2100).  Possibly, this will cause increasingly large variations with time for West Coast regional SLR superimposed on an accelerating eustatic SLR trend line.
« Last Edit: February 13, 2014, 06:44:07 PM by AbruptSLR »
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #154 on: February 19, 2014, 02:36:12 AM »
Related to the linear nature of the measured SLR from 1992 to 2013 shown by the University of Colorado in reply 151 and by AVISO in reply 152; given the non-linear nature of sea level contributors indicated by AR5, by the two attached figures.  The first attached AR5 image shows that SLR contribution from glaciers has been decelerating while the ice sheet contribution has been accelerating, in this timeframe.  The second attached AR5 image confirms that both the ice sheet SLR contribution, and the steric SLR contribution, have both been accelerating, while the land water store has been a negative SLR contribution that varies non-linearly with time.  I think that the linear nature of the measured eustatic SLR will have a positive acceleration beginning with the beginning of the next positive PDO cycle (possibly in the 2014-2015 timeframe):
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #155 on: February 28, 2014, 05:11:38 PM »
The attached regional sea level trend map (with not GIA correction) from Aviso (up to August 2013), clearly indicates that the rate of SLR in the ASE is equal to, or exceeding the mean global rate of SLR; which of course means that the glaciers in this area are becoming less stable:
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #156 on: March 05, 2014, 01:05:46 AM »
The following four Modis/Terra images of the Ferrigno Glacier Ice Tongue show: (a) on January 12 2014 the ice tongue has recently calved; (b) by Feb 1 2014 the ice tongue has re-extended; (c) on February 22 2014 the ice tongue has recently calved, and (d) by March 4 2014 the ice tongue has re-extended.  The Ferrigno Glacier Ice Tongue exhibited similar behavior in 2013 as can be seen in replay #16 of this thread.  These images indicate that the Ferrigno Ice Tongue is subject to relatively dynamic ocean-ice interaction, and that the glacier must be thinning actively near its gateway.
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #157 on: March 05, 2014, 01:08:10 AM »
For those who are interested, here is an image of the Ferrigno Glacier Ice Tongue from January 5 2014 before it calved (sometime between Jan 5 & Jan 12)
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #158 on: March 20, 2014, 11:35:40 PM »
The attached University of Colorado SLR graph for March 20 2014, shows that sea level is rising again; which in my opinion may mean that we are entering into a Strong El Nino year:
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #159 on: May 09, 2014, 12:22:43 AM »
The following linked reference indicates that the Whillans Ice Stream is not slowing down, but rather its ice flow rate varies through time including on interannual time scales:

Beem, L. H., S. M. Tulaczyk, M. A. King, M. Bougamont, H. A. Fricker, and P. Christoffersen (2014), "Variable deceleration of Whillans Ice Stream, West Antarctica", J. Geophys. Res. Earth Surf., 119, 212–224, doi:10.1002/2013JF002958.

http://onlinelibrary.wiley.com/doi/10.1002/2013JF002958/abstract

Abstract: "The Whillans Ice Stream Ice Plain (WIP) has been slowing since at least 1963. Prior constraints on this slowdown were consistent with a constant long-term deceleration rate. New observations of ice velocity from 11 continuous and 3 seasonal GPS sites indicate the deceleration rate varies through time including on interannual time scales. Between 2009 and 2012 WIP decelerated at a rate (6.1 to 10.9 ± 2 m/yr2) that was double the multidecadal average (3.0 to 5.6 ± 2 m/yr2). To identify the causes of slowdown, we used new and prior velocity estimates to constrain longitudinal and transverse force budget models as well as a higher-order inverse model. All model results support the conclusion that the observed deceleration of WIP is caused by an increase in basal resistance to motion at a rate of 10 to 40 Pa/yr. Subglacial processes that may be responsible for strengthening the ice stream bed include basal freeze on, changes in subglacial hydrology, or increases in the area of resistant basal substrate through differential erosion. The observed variability in WIP deceleration rate suggests that dynamics in subglacial hydrology, plausibly driven by basal freeze on and/or activity of subglacial lakes, plays a key role in modulating basal resistance to ice motion in the region."
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Re: Surge of WAIS Ice Mass Loss
« Reply #160 on: May 09, 2014, 04:29:36 PM »
I wasn't sure where to repost this. It was just posted on ASIB and I thought it may be of use here as it discusses the impact that Antarctic ice melt has on ocean currents.

http://www.dailykos.com/story/2014/03/05/1281907/-The-Antarctic-Half-of-the-Global-Thermohaline-Circulation-is-Collapsing

It seems to go a long way towards explaining the increase in Antarctic sea ice and seems to suggest that this might continue while we warm.

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #161 on: May 11, 2014, 11:28:45 PM »
While I believe that the linked reference (with a free access pdf of the paper) will make a valuable contribution to sea-level rise, SLR, projections; should the WAIS reach a tipping point after the 2030 end of the study, then the projections may well be non-conservative from a public safety point of view:

Ivan D. Haigh, Thomas Wahl, Eelco J. Rohling, René M. Price, Charitha B. Pattiaratchi, Francisco M. Calafat & Sönke Dangendorf, (2014), "Timescales for detecting a significant acceleration in sea level rise", Nature Communications 5, Article number: 3635 doi:10.1038/ncomms4635

http://www.nature.com/ncomms/2014/140414/ncomms4635/full/ncomms4635.html

Abstract: "There is observational evidence that global sea level is rising and there is concern that the rate of rise will increase, significantly threatening coastal communities. However, considerable debate remains as to whether the rate of sea level rise is currently increasing and, if so, by how much. Here we provide new insights into sea level accelerations by applying the main methods that have been used previously to search for accelerations in historical data, to identify the timings (with uncertainties) at which accelerations might first be recognized in a statistically significant manner (if not apparent already) in sea level records that we have artificially extended to 2100. We find that the most important approach to earliest possible detection of a significant sea level acceleration lies in improved understanding (and subsequent removal) of interannual to multidecadal variability in sea level records."
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Re: Surge of WAIS Ice Mass Loss
« Reply #162 on: May 12, 2014, 09:29:41 PM »
NASA-UCI Study Indicates Loss of West Antarctic Glaciers Appears Unstoppable
Quote
The study presents multiple lines of evidence, incorporating 40 years of observations that indicate the glaciers in the Amundsen Sea sector of West Antarctica "have passed the point of no return,"...
Three major lines of evidence point to the glaciers' eventual demise: the changes in their flow speeds, how much of each glacier floats on seawater, and the slope of the terrain they are flowing over and its depth below sea level.
Quote
"The collapse of this sector of West Antarctica appears to be unstoppable," he said. "The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable."

Because of the importance of this part of West Antarctica, NASA's Operation IceBridge will continue to monitor its evolution closely during this year's Antarctica deployment, which begins in October....
http://www.nasa.gov/press/2014/may/nasa-uci-study-indicates-loss-of-west-antarctic-glaciers-appears-unstoppable/
 
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RaenorShine

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Re: Surge of WAIS Ice Mass Loss
« Reply #163 on: May 13, 2014, 10:23:19 AM »
This has been picked up by BBC News also,

http://www.bbc.co.uk/news/science-environment-27381010

Quote
Key glaciers in West Antarctica are in an irreversible retreat, a study team led by the US space agency (Nasa) says.

It analysed 40 years of observations of six big ice streams draining into the Amundsen Bay and concluded that nothing now can stop them melting away.

Although these are abrupt changes, the timescales involved are likely measured in centuries, the researchers add.

Nick_Naylor

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Re: Surge of WAIS Ice Mass Loss
« Reply #164 on: May 13, 2014, 01:12:19 PM »
They recorded the press announcement, and with extended Q&A's.

http://www.ustream.tv/recorded/47484934

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Re: Surge of WAIS Ice Mass Loss
« Reply #165 on: May 13, 2014, 04:37:42 PM »
Not to appear to be a Jeremiah, but as important as the announcement that the ice mass loss of the glaciers in the ASE has been demonstrated by computer models to now be unstoppable, I point out that these computer model projections should be viewed as lower bound solutions, and that the researchers have not established an upper bound on the rate of ice mass loss from this area as their computer models cannot accurately represent such a potentially high degree of non-linear behavior.

Therefore, is it likely that we will not have a reasonable idea of the upper bound ice mass loss behavior is for the ASE (and for all of WAIS) until the end of the current positive PDO phase, sometime between 2030 and 2035, due to the potentially strong effect that a series of strong El Nino events may have on both the rate of grounding line retreat, and calving, from the ASE glaciers/ice shelves.  Which raises the possibility of abrupt sea level rise, ASLR, this century; we can all either wait and see what happens, or we can try to prepare adaptive measures to guard against the consequences of possibly unstoppable ASLR this century.

« Last Edit: May 13, 2014, 04:49:42 PM by AbruptSLR »
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Re: Surge of WAIS Ice Mass Loss
« Reply #166 on: May 13, 2014, 04:47:23 PM »
1st comment (I think) on ASIF.

Thanks to a comment by BaltimoreBrian on Dr. Jeff Master's blog at Weather Underground, I just read the original (?) major paper on WAIS collapse by Mercer in 1978.  If the new results hold, it seems that Dr. Mercer's prediction and analysis was quite amazingly accurate. Either way, it was a great intro read for me, and stunning that it was published more than 35 years ago.

https://courses.seas.harvard.edu/climate/eli/Courses/global-change-debates/Sources/18-West-Antarctic-ice-sheets/nature_mercer_1978_wais.pdf

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #167 on: June 30, 2014, 03:43:42 AM »
The linked reference (with a free access pdf) provides another estimate of ice mass loss from the Antarctic Peninsula and the WAIS; which indicates that some portions of the WAIS is gaining mass due to snowfall:

N. Schön, A. Zammit-Mangion, J. L. Bamber, J. Rougier, T. Flament, F. Rémy, and S. B. Luthcke,  (2014), "Simultaneous solution for mass trends on the West Antarctic Ice Sheet", The Cryosphere Discuss., 8, 2995–3035, doi:10.5194/tcd-8-2995-2014

http://www.the-cryosphere-discuss.net/8/2995/2014/tcd-8-2995-2014-print.pdf

Abstract: "The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last two decades in the West Antarctic Ice Sheet (WAIS), but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous, error-bounded trend estimate of ice mass loss over the WAIS from 2003–2009 which is almost entirely data-driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate, which can be used to validate and test the models. In addition, full spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of −76±15GTyr−1 for the WAIS and Antarctic Peninsula (AP), including the major Antarctic Islands. The GIA estimate compares very well with results obtained from recent forward models (IJ05-R2) and inversion methods (AGE-1). Due to its computational efficiency, the method is sufficiently scalable to include the whole of Antarctica, can be adapted for other ice sheets and can easily be adapted to assimilate data from other sources such as ice cores, accumulation radar data and other measurements that contain information about any of the processes that are solved for."
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steve s

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Re: Surge of WAIS Ice Mass Loss
« Reply #168 on: June 30, 2014, 06:37:57 AM »
" In this study, we provide a statistically rigorous, error-bounded trend estimate of ice mass loss over the WAIS from 2003–2009 which is almost entirely data-driven."

These results are necessarily biased downward by the estimation procedure. Or, more precisely, are determined entirely by the trends during the estimation period and the choice of observations used. You can judge whether you feel the observation period is likely to be indicative of future melting.

AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #169 on: June 30, 2014, 02:58:19 PM »
steve s,

I concur with you, that at the very least the period from 2003-2009 may not be indicative of the whole picture.  Nevertheless, I did not want to withhold information from people who hopefully can combine the information in this paper with other information in order to get a more comprehensive picture.

Best,
ASLR
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Re: Surge of WAIS Ice Mass Loss
« Reply #170 on: July 07, 2014, 05:46:50 PM »
Bedmap research is fundamental to determining the stability of Antarctic Ice Sheets, and the linked reference represents an incremental improvement on the state-of-the-art:

Christian Hirt, (2014), "GOCE's view below the ice of Antarctica: Satellite gravimetry confirms improvements in Bedmap2 bedrock knowledge, Geophysical Research Letters, DOI: 10.1002/2014GL060636

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060636/abstract

Abstract: "Accurate knowledge of Antarctica's topography, bedrock and ice sheet thickness is pivotal for climate change and geoscience research. Building on recent significant progress made in satellite gravity mapping with ESA's GOCE mission, we here reverse the widely used approach of validating satellite gravity with topography and instead utilize the new GOCE gravity maps for novel evaluation of Bedmap1/2. Space-collected GOCE gravity reveals clear improvements in the Bedmap2 ice and bedrock data over Bedmap1 via forward-modelled topographic mass and gravity effects at spatial scales of 400 to 80 km. Our study demonstrates GOCE's sensitivity for the subsurface mass distribution in the lithosphere, and delivers independent evidence for Bedmap2's improved quality reflecting new radar-derived ice thickness data. GOCE and Bedmap2 are combined to produce improved Bouguer gravity maps over Antarctica. We recommend incorporation of Bedmap2 in future high-resolution global topography and geopotential models, and its use for detailed geoid modelling over Antarctica."
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #171 on: July 07, 2014, 08:15:28 PM »
The attached image comes from the linked reference.  Per the caption below, this image shows CyroSat-2 data from 2010 to 2013 showing how rapidly the surface ice elevation has changed in the ASE marine glaciers, recently.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL060111/pdf


Caption: "Surface elevation change of the Amundsen Sea sector, West Antarctica, determined from CryoSat-2 (2010 to 2013) and, overlaid, from repeat airborne laser altimetry gridded at 5 km spacing (2009 to 2012) (see supporting information).  White boundaries delineate the drainage basins of the Pine Island Glacier (PIG), the Thwaites Glacier (THW), and the Pope/Smith/Kohler glaciers (PSK). (inset)  Distribution of the difference (CryoSat minus airborne) between 495 coincident CryoSat and airborne elevation rates, after accounting for a 15% bias introduced by the irregular sampling pattern of the airborne measurements (see supporting information). The root-mean-square difference in elevation rate determined using the CryoSat and airborne measurements is 54 cm yr_1; 21cmyr_1 of which can be explained by the airborne sampling bias, and the remainder can be explained by either a fluctuation in snow accumulation due to the 1 year mismatch in observation period (38 cm yr_1, based on the data in Table 1) or the uncertainties of the airborne and satellite measurements themselves (17 and 16 cm yr_1, respectively)."
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #172 on: August 31, 2014, 07:34:50 PM »
The linked web-article about the new Craig Rye et al (2014) publication in Nature Geoscience, indicates (see extracts below) that the local sea level in the Southern Ocean is increasing primarily due to the freshening of the local ocean due to local melting of ice shelves and ice sheets.  Obviously, increasing local sea levels serve to de-stabilize the marine glaciers in Antarctica, which acts as a positive feedback mechanism for further ice mass loss from Antarctic marine glaciers (such as PIG & Thwaites):

Craig Rye, et al, (2014), "Rapid sea-level rise along the Antarctic margins in response to increased glacial discharge", Nature Geoscience: dx.doi.org/10.1038/ngeo2230

http://www.businessinsider.com.au/sea-levels-are-rising-faster-in-the-antarctic-than-the-rest-of-the-world-2014-8

Extract: "Fresh water from melting glaciers has caused the sea level around the coast of Antarctica to rise by 2 centimetres more than the global average of 6 centimetres.

“Freshwater is less dense than salt water and so in regions where an excess of freshwater has accumulated we expect a localised rise in sea level,” says Craig Rye, lead author of the paper published in the journal Nature Geoscience.

The computer model supports our theory that the sea-level rise we see in our satellite data is almost entirely caused by freshening (a reduction in the salinity of the water) from the melting of the ice sheet and its fringing ice shelves,” says Craig."
« Last Edit: August 31, 2014, 07:43:07 PM by AbruptSLR »
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #173 on: November 24, 2014, 06:17:03 PM »
As a follow-up to Replies #100 to #102, NASA has released additional images of the 2013 & 2012 Antarctic IceBridge campaigns that can be found at:

ftp://n5eil01u.ecs.nsidc.org/SAN2/ICEBRIDGE/IRMCR1B.002/

As I am most concerned (and as this thread is focused on) a possible surge of ice through the Thwaites Gateway area; images from the 2012 campaign in the Thwaites Gateway area can be found here:

ftp://n5eil01u.ecs.nsidc.org/SAN2/ICEBRIDGE/IRMCR1B.002/2012.10.12/

Also, the four attached images are plans and (echogram) profiles for the Eastern Thwaites Ice Shelf, and the Thwaites Ice Tongue, Ground-lines areas, respectively:
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wili

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Re: Surge of WAIS Ice Mass Loss
« Reply #174 on: December 02, 2014, 10:35:18 PM »
(Thanks to Graeme at POForums for this link)

West Antarctic Ice Sheet Melt Rate Tripled Says Research

   
Quote
A comprehensive, 21-year analysis of the fastest-melting region of Antarctica has found that the melt rate of glaciers there has tripled during the last decade.

    The glaciers in the Amundsen Sea Embayment in West Antarctica are hemorrhaging ice faster than any other part of Antarctica and are the most significant Antarctic contributors to sea level rise. This study by scientists at the University of California, Irvine (UCI), and NASA is the first to evaluate and reconcile observations from four different measurement techniques to produce an authoritative estimate of the amount and the rate of loss over the last two decades.

    “The mass loss of these glaciers is increasing at an amazing rate," said scientist Isabella Velicogna, jointly of UCI and NASA's Jet Propulsion Laboratory, Pasadena, California. Velicogna is a coauthor of a paper on the results, which has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

http://www.reportingclimatescience.com/news-stories/article/west-antarctic-ice-sheet-melt-rate-tripled-says-research.html
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sidd

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Re: Surge of WAIS Ice Mass Loss
« Reply #175 on: December 03, 2014, 10:11:12 PM »
Re: Sutterley(2014) doi:10.1002/2014GL061940

1)remarkable agreement between all methods, fig2
2)acceleration of mass loss triples in two decades
3)Grace data thru 2014 summer

2) is consistent with faster than quadratic mass waste. 
« Last Edit: December 04, 2014, 06:13:42 AM by sidd »

Lennart van der Linde

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Re: Surge of WAIS Ice Mass Loss
« Reply #176 on: December 05, 2014, 08:47:10 AM »
Also see comments by Rignot:
http://www.washingtonpost.com/national/health-science/research-casts-alarming-light-on-decline-of-west-antarctic-ice-sheets/2014/12/04/19efd3e4-7bbe-11e4-84d4-7c896b90abdc_story.html

He thinks one third of WAIS may be gone in 100-200 years. That would be about a meter extra SLR on top of current IPCC projections, so in total maybe close to 1.5-2.0 meters in 2100-2014, in the worst-case?

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Re: Surge of WAIS Ice Mass Loss
« Reply #177 on: December 05, 2014, 02:09:27 PM »
Does an extra 1m of SLR have consequences in terms of making other losses inevitable or is it only this area of grounded below sea level ice sheet vulnerable to this?

Making outlets from Greenland deeper and wider isn't going to help, so IPCC 1m high end should only increase but maybe this is only marginal and not really a tipping point into making more losses inevitable?


Lennart van der Linde

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Re: Surge of WAIS Ice Mass Loss
« Reply #178 on: December 05, 2014, 09:13:55 PM »
I think Totten glacier may also be at risk in the longer term, but less is known about this and other EAIS-marine based glaciers.

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Re: Surge of WAIS Ice Mass Loss
« Reply #179 on: December 05, 2014, 09:40:05 PM »
So Rignot has come out and said it, a third of WAIS gone in one or two centuries. The next two thirds will go even faster. Feldman (open access, doi:10.5194/tcd-8-4885-2014) shows how destabilizing one basin destabilizes others.

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Re: Surge of WAIS Ice Mass Loss
« Reply #180 on: December 06, 2014, 09:12:17 AM »
Thanks, sidd, for referring to Feldmann & Levermann 2014:
http://www.the-cryosphere-discuss.net/8/4885/2014/tcd-8-4885-2014.html

Interaction of marine ice-sheet instabilities in two drainage basins: simple scaling of geometry and transition time

Abstract
Recent regional simulations and observations suggest a destabilization of the Amundsen Sea sector of West Antarctica. Whether the initiated ice drainage will be limited to Pine Island and Thwaites basin or extend to the Filchner–Ronne basin depends on the possibility of an interaction of the different drainage basins. Using a conceptional flow-line geometry, we investigate the possibility of whether a marine ice-sheet instability (MISI) can be triggered from the direction of the ice divide as opposed to coastal forcing and investigate the interaction between connected basins. We find that the initiation of a MISI in one basin can induce a destabilization in the other. The underlying mechanism of basin interaction is based on dynamic thinning and a consecutive motion of the ice divide which induces a thinning in the adjacent basin and a successive initiation of the instability. Our simplified and symmetric topographic set-up allows to scale both the geometry and the transition time between both instabilities. We find that the ice profile follows a universal shape that is scaled with the horizontal extent of the ice sheet and that the same exponent of 1/2 applies for the scaling relation between central surface elevation and horizontal extent as in the pure Shallow Ice Approximation (Vialov profile). Altering the central bed elevation we find that the extent of grounding line retreat in one basin determines the degree of interaction with the other. We conclude that for the three-dimensional case the possibility of such drainage basin interaction cannot be excluded and hence needs further investigation.

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Re: Surge of WAIS Ice Mass Loss
« Reply #181 on: December 06, 2014, 10:46:32 AM »
Mengel & Levermann 2014 indicates the vulnerability of the EAIS Wilkes Basin:
http://www.pik-potsdam.de/~anders/publications/mengel_levermann14.pdf

Ice plug prevents irreversible discharge from East Antarctica

Abstract
Changes in ice discharge from Antarctica constitute the largest uncertainty in future sea-level projections, mainly because of the unknown response of its marine basins. Most of West Antarctica’s marine ice sheet lies on an inland-sloping bed and is thereby prone to a marine ice sheet instability. A similar topographic configuration is found in large parts of East Antarctica, which holds marine ice equivalent to 19m of global sea-level rise, that is, more than five times that of West Antarctica. Within East Antarctica, the Wilkes Basin holds the largest volume of marine ice that is fully connected by subglacial troughs. This icebody was significantly reduced during the Pliocene epoch. Strong melting underneath adjacent ice shelves with similar bathymetry indicates the ice sheet’s sensitivity to climatic perturbations. The stability of the Wilkes marine ice sheet has not been the subject of any comprehensive assessment of future sea level. Using recently improved topographic data in combination with ice-dynamic simulations, we show here that the removal of a specific coastal ice volume equivalent to less than 80mm of global sea-level rise at the margin of the Wilkes Basin destabilizes the regional ice flow and leads to a self-sustained discharge of the entire basin and a global sea-level rise of 3–4m. Our results are robust with respect to variation in ice parameters, forcing details and model resolution as well as increased surface mass balance, indicating that East Antarctica may become a large contributor to future sea-level rise on times cales beyond a century.

Lennart van der Linde

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Re: Surge of WAIS Ice Mass Loss
« Reply #182 on: December 06, 2014, 11:06:38 AM »
Also relevant from the EAIS-thread:

Fogwill, C., C. Turney, K. Meissner, N. Golledge, P. Spence , J. Roberts, M. England, L. Carter, (2014), Testing the sensitivity of the East Antarctica Ice Sheet to Southern Ocean dynamics: past changes and future implications, Journal of Quaternary Science, 29 (1), 91-98, DOI: 10.1002/jqs.2683

http://onlinelibrary.wiley.com/doi/10.1002/jqs.2683/pdf

ABSTRACT
The stability of Antarctic ice sheets and their potential contribution to sea level under projected future warming remains highly uncertain. The Last Interglacial (135 000–116 000 years ago) provides a potential analogue, with global temperatures 2 °C higher and rates of sea-level rise >5.6m ka_1, leading to sea levels 6.6– 9.4m higher than present. The source(s) of this sea-level rise remain fiercely debated. Here we report a series of independent model simulations exploring the effects of migrating Southern Hemisphere Westerlies (SHWs) on Southern Ocean circulation and Antarctic ice-sheet dynamics. We suggest that southerly shifts in winds may have significantly impacted the sub-polar gyres, inducing pervasive warming (0.2–0.8 °C in the upper 1200 m) adjacent to sectors of the East Antarctic Ice Sheet (EAIS), which due to their geometries and connectivity to the Southern Ocean are highly sensitive to ocean forcing. We conclude that the EAIS potentially made a substantial, hitherto unsuspected, contribution to interglacial sea levels, and given 21st-century projections in the Southern Annular Mode and associated SHW migration, we highlight how pervasive circum-Antarctic warming may threaten EAIS stability.
« Last Edit: December 06, 2014, 02:41:04 PM by Lennart van der Linde »

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Re: Surge of WAIS Ice Mass Loss
« Reply #183 on: December 06, 2014, 02:50:37 PM »
Fogwill et al 2014 conclude:

"In summary, we propose that the EAIS may provide an important missing component of LIG SLR, reconciling empirical geological (Kopp et al., 2009; Dutton and Lambeck, 2012) and model-based estimates. Specifically, we suggest that local ocean warming off the Weddell and Ross seas and in Prydz Bay, associated with a poleward shift in SHWs, led to accelerated mass loss from specific sectors of the EAIS, resulting in a 3–5m contribution to SLR at the LIG. Ice-sheet modelling experiments suggest that sectors of the EAIS which exhibit concave profiles (characteristic of weaker bed conditions) are more susceptible to higher potential mass flux rates, making them highly sensitive to ocean forcing. These areas of sensitivity are not necessarily the deepest basins of the EAIS, which have been previously proposed as being vulnerable to ocean-driven instabilities (Fox, 2010)."

So even before the Wilkes and Aurora basins will start to lose more ice, less deep basins at the other side of EAIS may start to contribute significantly to SLR.

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Re: Surge of WAIS Ice Mass Loss
« Reply #184 on: December 06, 2014, 03:29:19 PM »
Khazendar et al 2014 on Totten Glacier:
http://www.staff.science.uu.nl/~broek112/home.php_files/Publications_MvdB/2013_Khazendar_NatComm.pdf

Observed thinning of Totten Glacier is linked to coastal polynya variability

Abstract
Analysis of ICESat-1 data (2003–2008) shows significant surface lowering of Totten Glacier, the glacier discharging the largest volume of ice in East Antarctica, and less change on nearby Moscow University Glacier. After accounting for firn compaction anomalies, the thinning appears to coincide with fast-flowing ice indicating a dynamical origin. Here, to elucidate these observations, we apply high-resolution ice–ocean modelling. Totten Ice Shelf is simulated to have higher, more variable basal melting rates. We link this variability to the volume of cold water, originating in polynyas upon sea ice formation, reaching the sub-ice-shelf cavity. Hence, we propose that the observed increased thinning of Totten Glacier is due to enhanced basal melting caused by a decrease in cold polynya water reaching its cavity. We support this hypothesis with passive microwave data of polynya extent variability. Considering the widespread changes in sea ice conditions, this mechanism could be contributing extensively to ice-shelf instability.

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Re: Surge of WAIS Ice Mass Loss
« Reply #185 on: December 07, 2014, 01:47:11 AM »
For viewing purposes as context for above posts.

Lennart van der Linde

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Re: Surge of WAIS Ice Mass Loss
« Reply #186 on: December 07, 2014, 07:48:56 AM »
And another one with names and ice velocities:

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Re: Surge of WAIS Ice Mass Loss
« Reply #187 on: December 09, 2014, 04:21:17 AM »
This is an interesting NOVA doc focused mainly on the WAIS, but does give indications that the EAIS was also involved in the last melt era.
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #188 on: July 07, 2015, 02:10:20 AM »
The linked reference (with an open access pdf) uses a hierarchical Bayesian framework to derive key ice mass loss parameters (like GIA) from the WAIS using field data from 2003 to 2009.

Schoen, N., Zammit-Mangion, A., Rougier, J. C., Flament, T., Rémy, F., Luthcke, S., and Bamber, J. L.: Simultaneous solution for mass trends on the West Antarctic Ice Sheet, The Cryosphere, 9, 805-819, doi:10.5194/tc-9-805-2015, 2015.

http://www.the-cryosphere.net/9/805/2015/tc-9-805-2015.html
http://www.the-cryosphere.net/9/805/2015/tc-9-805-2015.pdf

Abstract: "The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last 2 decades for the West Antarctic Ice Sheet (WAIS) but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous error-bounded trend estimate of ice mass loss over the WAIS from 2003 to 2009 which is almost entirely data driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate which can be used to validate and test the models. In addition, spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of −76 ± 15 Gt yr−1 for the WAIS and Antarctic Peninsula, including the major Antarctic islands. The GIA estimate compares well with results obtained from recent forward models (IJ05-R2) and inverse methods (AGE-1). The Bayesian framework is sufficiently flexible that it can, eventually, be used for the whole of Antarctica, be adapted for other ice sheets and utilise data from other sources such as ice cores, accumulation radar data, and other measurements that contain information about any of the processes that are solved for."
« Last Edit: August 04, 2015, 08:05:35 PM by AbruptSLR »
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #189 on: September 12, 2016, 10:54:51 PM »
The following is an update on ice velocity variation for the PIIS from 2000 thru 2014:

Hyangsun Han, Jungho Im & Hyun-cheol Kim (2016), "Variations in ice velocities of Pine Island Glacier Ice Shelf evaluated using multispectral image matching of Landsat time series data", Remote Sensing of Environment, Volume 186, Pages 358–371, http://dx.doi.org/10.1016/j.rse.2016.09.001

http://www.sciencedirect.com/science/article/pii/S0034425716303443

Abstract: "Pine Island Glacier (PIG) in West Antarctica drains out to the Amundsen Sea through Pine Island Glacier Ice Shelf (PIGIS). As changes in ice velocities on PIGIS are strongly linked to changes in ice mass discharge from the West Antarctic Ice Sheet, it is very important to evaluate the spatiotemporal variations in ice velocities on the ice shelf. This research estimated ice velocities of PIGIS from an ensemble of image matching of Landsat time series multispectral data obtained from 2000 to 2014. Orientation correlation was adopted for the image matching of blue, green, red, near infrared, panchromatic, and the first principal image of the Landsat multispectral data, from which the results were combined and averaged. The multispectral image matching proposed in this research produced ~ 35% more ice velocity vectors than the use of a single band (i.e., panchromatic band) image matching. The erroneous matches were filtered through simple but rigorous statistical evaluations. The ice velocity of PIGIS accelerated by ~ 55% during 2000–2010, and the acceleration of the image northing velocity component (~ 1.3 km a− 1) was higher than that of the image easting velocity component (~ 0.8 km a− 1). During 2010–2012, the ice velocity of PIGIS slowed down by ~ 10%. The ice velocity in 2014 increased by 5% from 2012, but was still lower than the peak values observed in 2010. The surface strain rate fields of PIGIS were derived from the ice velocity fields. The longitudinal ice compression was observed near the grounding line and the geographically northern part of the central ice shelf of PIGIS, while a fast-flowing band was observed near the southern margin of the ice shelf. The transverse strain rate showed that ice divergence in the hinge zone of the central ice shelf has increased since 2000. The width of the shear margins of the central ice shelf of PIGIS is ~ 25 km, which has been stable since 2000."

Highlights
• A multispectral image matching technique was developed for deriving ice velocities.
• Advantages of the developed multispectral image matching technique were demonstrated.
• Velocities of Pine Island Glacier Ice Shelf (PIGIS) during 2000–2014 were evaluated.
• PIGIS accelerated during 2000–2010 by ~ 55% and decelerated during 2010–2012 by ~ 10%.
• Velocities of PIGIS in 2014 increased by 5% from 2012, but were below those in 2010.
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #190 on: October 20, 2016, 01:27:10 AM »
The US & the UK are planning a surge of research over a 5 year period to improve projections of the stability of the Thwaites Glacier


http://www.sciencemag.org/news/2016/10/us-and-uk-plan-thwaites-invasion-antarctica

Extract: "If there's one universal question that scientists working on the West Antarctic Ice Sheet hear from their friends and families, it's this: "How fast is the sea going to rise?"
The ice sheet is one of the biggest wild cards in sea-level projections for the next century, its durable uncertainty complicating efforts to adapt to human-driven climate change. Once thought stable for centuries, it has become clear from satellite and airplane observations that parts of the sheet are thinning and could become unstable. But when that might happen is uncertain, with estimates ranging from as soon as the next few decades to the next few centuries.
In a bid to refine these estimates, this month the National Science Foundation (NSF) and the United Kingdom's Natural Environment Research Council will announce a project to support coordinated fieldwork on the Thwaites Glacier, the emerging epicenter of potential melt on the West Antarctic Ice Sheet. Although NSF declined to disclose exact figures, the initiative will likely provide tens of millions of dollars for Antarctic research over 5 years, including spending on infrastructure.
The "Thwaites invasion" will be "the biggest thing to happen in our area of science for quite a long time," said David Vaughan, director of science at the British Antarctic Survey in Cambridge at an annual interdisciplinary workshop for West Antarctic scientists held here this week. The initiative will be expected to feed data directly into the sea-level forecasts produced by the Intergovernmental Panel on Climate Change. "We want real outcomes that improve projections," he said."
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oren

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Re: Surge of WAIS Ice Mass Loss
« Reply #191 on: October 20, 2016, 12:03:13 PM »
Does anyone know if there are any direct measurements of ocean temps (and salinity) at depth near PIG and Thwaites? I would imagine a long-term view of such temps would help to answer many questions.

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Re: Surge of WAIS Ice Mass Loss
« Reply #192 on: October 22, 2016, 06:23:46 PM »
The linked article elaborates on the newly announce joint NSF-NERC's initiative to focus on the Thwaites Glacier's ability to contribute to abrupt sea level rise this century.

https://www.washingtonpost.com/news/energy-environment/wp/2016/10/21/scientists-just-showed-what-it-truly-means-when-a-huge-antarctic-glacier-is-unstable/?tid=a_inl&utm_term=.2c0d915bf9d4

Extract: "On Thursday, the National Science Foundation and the U.K.’s Natural Environment Research Council made a joint announcement signaling how grave this really is — they will fund a multi-million dollar research initiative to the less-studied Thwaites, in order to determine just how much it is capable of contributing to sea level rise during our lifetimes, and by the end of the century."
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Re: Surge of WAIS Ice Mass Loss
« Reply #193 on: October 22, 2016, 07:38:41 PM »
This link is to a post with a nice picture of the area back in 2011 from page 1.
Here is a gif from Sep 22 to Oct 21.  It looks to me that there is quite a bit of crack propagation in the bottom right corner, should be an interesting summer.
http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20161021T045158_48ED_S_1.final.jpg

S1A_EW_GRDM_1SSH_20160922T044353_102C_S_1.final.jpg
« Last Edit: October 22, 2016, 07:45:15 PM by solartim27 »
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Re: Surge of WAIS Ice Mass Loss
« Reply #194 on: October 25, 2016, 05:45:05 PM »
This article seems to be very similiar to the one posted by ASLR in #189 just above.  Does not seem to be anything new to me.  First noticed the NPR story, could not find the nature.com link in the article, just a 404 error.  These other articles are linked in the story as well, one current, one is from 2014:
http://www.npr.org/sections/thetwo-way/2016/10/25/499206005/antarcticas-ice-sheets-are-melting-faster-and-from-beneath?utm_medium=RSS&utm_campaign=news

(Both are paywalled)
http://onlinelibrary.wiley.com/doi/10.1002/2016GL070500/full
Quote
We present subannual observations (2009–2014) of a major West Antarctic glacier (Pine Island Glacier) and the neighboring ocean. Ongoing glacier retreat and accelerated ice flow were likely triggered a few decades ago by increased ocean-induced thinning, which may have initiated marine ice-sheet instability. Following a subsequent 60% drop in ocean heat content from early 2012 to late 2013, ice flow slowed, but by < 4%, with flow recovering as the ocean warmed to prior temperatures. During this cold-ocean period, the evolving glacier-bed/ice-shelf system was also in a geometry favorable to stabilization. However, despite a minor, temporary decrease in ice discharge, the basin-wide thinning signal did not change. Thus, as predicted by theory, once marine ice-sheet instability is underway, a single transient high-amplitude ocean cooling has only a relatively minor effect on ice flow. The long-term effects of ocean-temperature variability on ice flow, however, are not yet known.

http://science.sciencemag.org/content/344/6185/735
Quote
Resting atop a deep marine basin, the West Antarctic Ice Sheet has long been considered prone to instability. Using a numerical model, we investigated the sensitivity of Thwaites Glacier to ocean melt and whether its unstable retreat is already under way. Our model reproduces observed losses when forced with ocean melt comparable to estimates. Simulated losses are moderate (<0.25 mm per year at sea level) over the 21st century but generally increase thereafter. Except possibly for the lowest-melt scenario, the simulations indicate that early-stage collapse has begun. Less certain is the time scale, with the onset of rapid (>1 mm per year of sea-level rise) collapse in the different simulations within the range of 200 to 900 years.
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Re: Surge of WAIS Ice Mass Loss
« Reply #195 on: October 25, 2016, 07:49:05 PM »
Article linked to in the above NPR story is now up:

http://www.nature.com/articles/ncomms13243

Quote
Rapid submarine ice melting in the grounding zones of ice shelves in West Antarctica
Enhanced submarine ice-shelf melting strongly controls ice loss in the Amundsen Sea embayment (ASE) of West Antarctica, but its magnitude is not well known in the critical grounding zones of the ASE’s major glaciers. Here we directly quantify bottom ice losses along tens of kilometres with airborne radar sounding of the Dotson and Crosson ice shelves, which buttress the rapidly changing Smith, Pope and Kohler glaciers. Melting in the grounding zones is found to be much higher than steady-state levels, removing 300–490 m of solid ice between 2002 and 2009 beneath the retreating Smith Glacier. The vigorous, unbalanced melting supports the hypothesis that a significant increase in ocean heat influx into ASE sub-ice-shelf cavities took place in the mid-2000s. The synchronous but diverse evolutions of these glaciers illustrate how combinations of oceanography and topography modulate rapid submarine melting to hasten mass loss and glacier retreat from West Antarctica.
Quote
Pine Island (PIG) and Thwaites (TG) glaciers, the two largest in the ASE, merited much attention due to their present and possible future large contributions to sea level rise11,12,13. Yet, some of the most rapid changes in the region are being observed in the Dotson and Crosson ice shelves (Fig. 1a,b) and their main tributary glaciers of Smith (SG), Pope (PG) and Kohler (KG).
Edit, I made a gif of Crosson from the same Sentinal images above
http://www.polarview.aq/images/105_S1jpgfull/S1A_EW_GRDM_1SSH_20161021T045158_48ED_S_1.final.jpg
and S1A_EW_GRDM_1SSH_20160922T044353_102C_S_1.final.jpg
« Last Edit: October 25, 2016, 08:24:49 PM by solartim27 »
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AbruptSLR

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Re: Surge of WAIS Ice Mass Loss
« Reply #196 on: November 24, 2016, 02:03:00 AM »
The linked reference indicates that current retreat of the Pine Island Glacier began in 1945+/- 12 years:

J. A. Smith, T. J. Andersen, M. Shortt, A. M. Gaffney, M. Truffer, T. P. Stanton, R. Bindschadler, P. Dutrieux, A. Jenkins, C.-D. Hillenbrand, W. Ehrmann, H. F. J. Corr, N. Farley, S. Crowhurst & D. G. Vaughan (2016), “Sub-ice-shelf sediments record history of twentieth-century retreat of Pine Island Glacier”, Nature, doi:10.1038/nature20136


http://www.nature.com/nature/journal/vaop/ncurrent/full/nature20136.html

Abstract: “The West Antarctic Ice Sheet is one of the largest potential sources of rising sea levels.  Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line—which marks the boundary between grounded ice and floating ice shelf—is underway. Understanding this recent retreat requires a detailed knowledge of grounding-line history, but the locations of the grounding line before the advent of satellite monitoring in the 1990s are poorly dated. In particular, a history of grounding-line retreat is required to understand the relative roles of contemporaneous ocean-forced change and of ongoing glacier response to an earlier perturbation in driving ice-sheet loss. Here we show that the present thinning and retreat of Pine Island Glacier in West Antarctica is part of a climatically forced trend that was triggered in the 1940s. Our conclusions arise from analysis of sediment cores recovered beneath the floating Pine Island Glacier ice shelf, and constrain the date at which the grounding line retreated from a prominent seafloor ridge. We find that incursion of marine water beyond the crest of this ridge, forming an ocean cavity beneath the ice shelf, occurred in 1945 (±12 years); final ungrounding of the ice shelf from the ridge occurred in 1970 (±4 years). The initial opening of this ocean cavity followed a period of strong warming of West Antarctica, associated with El Niño activity. Thus our results suggest that, even when climate forcing weakened, ice-sheet retreat continued. “


See also:

http://www.nature.com/articles/nature20136.epdf?referrer_access_token=XfTyNuEKobU5twzDTLgrEtRgN0jAjWel9jnR3ZoTv0OUEdWVnLM6cbD9f3EvgiBS9a48ktZRob2XfCijxjYkNR2f3TavCkvoleRsfYA34T0dyKa2hhuWxvqPDDiSgGk38SuJeO5vOqFZgFJR64gCU50fz1RoBIdpHG0EItYAwXwqpW9_ZnrQMymqucD6Q1OdDKg-NpVLSiLnJpgjOGB0TS_qF0XQ2qYpuNmF7qwseGLpvAYPB2aJ1nYDsEsfvScXGAvMOWv-ESTCjFcaRrzU_bLLqOgjuBra2OxE6u-DDn9FZcNeigKwcRc4POgd715PO2nfrRg9uAOMlvRXyi2_w9E1R9jgyk4Pfn8IPTa5WPNFdgqX7Rc0n-XU1S5S7UnU&tracking_referrer=www.washingtonpost.com


&

https://www.washingtonpost.com/news/energy-environment/wp/2016/11/23/west-antarctica-is-in-big-trouble-but-now-scientists-say-that-may-date-back-to-1945/?utm_term=.396c72962169

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

Hefaistos

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Re: Surge of WAIS Ice Mass Loss
« Reply #197 on: December 12, 2016, 03:17:01 PM »
Article on the BBC today:

"The scale and pace of change now taking place in West Antarctica is captured in a new, long-term satellite record.

Scientists have combined nearly a quarter of a century of observations to show how the region's great glaciers are losing height by up to 7m per year.

The satellite data also traces the way this thinning behaviour has spread up the length of the ice streams.

As the glaciers accelerate, they have to take ever more ice from the interior to compensate for the speed-up. This means they thin; they lose height, which we can detect from space," explained Dr Hannes Konrad from the UK's Centre for Polar Observation and Monitoring (CPOM).

"And if there is no increase in snow and ice in the interior then this thinning will just migrate further and further upstream,"

http://www.bbc.com/news/science-environment-38256932

Article here (paywallled):
http://onlinelibrary.wiley.com/doi/10.1002/2016GL070733/full

Hefaistos

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Re: Surge of WAIS Ice Mass Loss
« Reply #198 on: December 12, 2016, 03:25:56 PM »
From the same BBC article, about PIG and Thwaites:

Pine Island Glacier (PIG), which currently contributes more to sea level rise than any other ice stream on the planet, thins fairly steadily and relentlessly.

The lowering of its surface is already in play by the start of the satellite measurements, and now spreads back from its grounding line, along its main trunk for hundreds of km inland.

At maximum, the glacier is losing 5m in height every year and the thinning spreads inland at up to 15km per year at times.

Thwaites, on the other hand, started dropping its elevation later than the PIG and did so in two broad periods. Its delayed and episodic response means thinning on Thwaites has not spread so far inland.

Buddy

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Re: Surge of WAIS Ice Mass Loss
« Reply #199 on: December 12, 2016, 06:35:58 PM »
Quote
Pine Island Glacier (PIG), which currently contributes more to sea level rise than any other ice stream on the planet, thins fairly steadily and relentlessly.

The lowering of its surface is already in play by the start of the satellite measurements, and now spreads back from its grounding line, along its main trunk for hundreds of km inland.

At maximum, the glacier is losing 5m in height every year and the thinning spreads inland at up to 15km per year at times.

WOW.....5 meters of thickness per year is a BUNCH.  Not good....... :'(
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