|Antarctic Ice Streams (from Dr. Rignot video below)|
This is the first time that Dredd Blog has posted two "Weekend Rebel" types of posts in one weekend.
I am doing so because a paper published on Friday, October 30, 2015, by NASA employees and contractors, is contrary to the general scientific consensus concerning ice sheet loss @ Antarctica.
It is also looks like a clone of a paper by the same title, written over three years earlier by the same lead author (Mass Gains of the Antarctic Ice Sheet Exceed Losses, PDF Version).
It appears that the author is doubling down on opinions held for a long time that fly in the face of current consensus science, and even the IPCC conservative consensus.
II. Current Consensus
For several years scientific papers have indicated that Antarctica is losing more ice from ice sheets (ice mass on land) than is replaced by annual snow fall:
Measurements from ESA’s CryoSat mission have been used to map the height of the huge ice sheets that blanket Greenland and Antarctica and show how they are changing. New results reveal combined ice volume loss at an unprecedented rate of 500 cubic kilometres a year.(ESA Cryosat, emphasis added). As to East Antarctica, there are indications that the largest ice stream, the Totten, is acting up too:
The resulting maps reveal that Greenland alone is reducing in volume by about 375 cubic kilometres a year.
The researchers say the ice sheets’ annual contribution to sea-level rise has doubled since 2009. [Table 1 type contribution - i.e. thermal sea level rise (additional) is not included in that doubling]
Glaciologist Angelika Humbert, another of the study’s authors, added, “Since 2009, the volume loss in Greenland has increased by a factor of about two and the West Antarctic Ice Sheet by a factor of three."
There is also a bigger picture than West Antarctica. The Amundsen sea sector is not the only vulnerable part of the continent. East Antarctica includes marine-based sectors that hold more ice. One of them, Totten glacier, holds the equivalent of seven metres of global sea level.(Climate Rocks, quoting Dr. Eric Rignot). More recently a paper published in Nature supports the notion of the East Antarctica Totten ice stream initial demise:
Totten Glacier, the primary outlet of the Aurora Subglacial Basin, has the largest thinning rate in East Antarctica. Thinning may be driven by enhanced basal melting due to ocean processes, modulated by polynya activity. Warm modified Circumpolar Deep Water, which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby continental shelf beneath 400 to 500 m of cool Antarctic Surface Water. Here we derive the bathymetry of the sea floor in the region from gravity9 and magnetics data as well as ice-thickness measurements. We identify entrances to the ice-shelf cavity below depths of 400 to 500 m that could allow intrusions of warm water if the vertical structure of inflow is similar to nearby observations. Radar sounding reveals a previously unknown inland trough that connects the main ice-shelf cavity to the ocean. If thinning trends continue, a larger water body over the trough could potentially allow more warm water into the cavity, which may, eventually, lead to destabilization of the low-lying region between Totten Glacier and the similarly deep glacier flowing into the Reynolds Trough. We estimate that at least 3.5 m of eustatic sea level potential drains through Totten Glacier, so coastal processes in this area could have global consequences.(Nature Geoscience, 2015, emphasis added). The ongoing reality has been detected in terms of loss of mass / gravity as well:
The onset of such rapid loss “came as a surprise to us," says Bert Wouters, a fellow at the University of Bristol in England, who led the analysis, published in the May 22 Science. In just a few years, he says, the dynamics of the region “completely shifted."(Scientific American). Ok, so there is a consensus that Antarctica is showing massive ice sheet mass / gravity loss.
The surface of some of the glaciers is dropping by as much as four meters each year, as measured by remote-sensing instruments on the CryoSat 2 satellite. The ice loss is so great it is also causing changes in Earth’s gravitational field, which have been detected by GRACE (Gravity Recovery and Climate Experiment) satellites.
But, that could be happening even if the annual snowfall was in fact increasing the ice mass in other places on Antarctica.
IMO, that would only mean that sea level change (SLC) in the form of sea level rise (SLR) would eventually take place for a longer period of time, a longer duration:
I even push it to the point that I am not sure I even care about precipitation patterns any more, as opposed to what the glaciers are doing at this point, caused by climate forcing. Precipitation is low on these ice sheets. They are deserts by, you know, Earth standards. The average precipitation on Earth is about a meter, here it snows ten times less in Greenland and Antarctica.(Dr. Rignot, video below @ 04:00). The issue of SLR or sea level fall (SLF) is not properly addressed by measuring how much snowfall Antarctica has.
Instead, the issue is properly addressed by measuring how much SLC is taking place caused by the Antarctic ice sheet mass / gravity loss.
III. The 2015 Version of the 2012 Paper
A paper published, on October 30, 2015, has the same title as the one published in 2012 by the same lead author (doubling down?).
Both papers argue that Antarctica is gaining more land ice due to snowfall than is being lost to melt and calving:
Mass changes of the Antarctic ice sheet impact sea-level rise as climate changes, but recent rates have been uncertain. Ice, Cloud and land Elevation Satellite (ICESat) data (2003–08) show mass gains from snow accumulation exceeded discharge losses by 82 ± 25 Gt a–1, reducing global sea-level rise by 0.23 mm a–1. European Remote-sensing Satellite (ERS) data (1992–2001) give a similar gain of 112 ± 61 Gt a–1. Gains of 136 Gt a–1 in East Antarctica (EA) and 72 Gt a–1 in four drainage systems (WA2) in West Antarctic (WA) exceed losses of 97 Gt a–1 from three coastal drainage systems (WA1) and 29 Gt a–1 from the Antarctic Peninsula (AP). EA dynamic thickening of 147 Gt a–1 is a continuing response to increased accumulation (>50%) since the early Holocene. Recent accumulation loss of 11 Gt a–1 in EA indicates thickening is not from contemporaneous snowfall increases. Similarly, the WA2 gain is mainly (60 Gt a–1) dynamic thickening. In WA1 and the AP, increased losses of 66 ± 16 Gt a–1 from increased dynamic thinning from accelerating glaciers are 50% offset by greater WA snowfall. The decadal increase in dynamic thinning in WA1 and the AP is approximately one-third of the long-term dynamic thickening in EA and WA2, which should buffer additional dynamic thinning for decades.(Mass gains of the Antarctic ice sheet exceed losses). The paper, as did the older version, cites to older studies prior to the 2013 IPCC consensus report.
In its analysis, it does not even mention the more recent Cryosat - 2, or GRACE, satellite projects.
The author admits that his paper, written before the IPCC released its 2013 consensus report, is contrary to that scientific consensus, as is his current paper released on Friday:
The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change's (IPCC) 2013 report, which says that Antarctica is overall losing land ice.(Science Daily, emphasis added). The latest paper, like the original, does not mention the work of Mitrivica et al. (see 2nd video below) concerning the ability to fingerprint SLC, including where the ice or melt water causing that SLC came from.
"The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away," Zwally said. "But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for."
That fingerprinting is being done by using global tide gauge station records from the Permanent Service for Mean Sea Level (PSMSL).
Errors in Dr. Zwally's latest paper begin from about the 2nd sentence:
In Greenland, surface melting in the ablation zone causes water runoff from the grounded ice and acceleration of the ice flow as meltwater propagates to the ice-sheet base to enhance basal sliding. In contrast, surface melting on the grounded ice of Antarctica is very small, and subject to refreezing in the firn, with negligible mass loss.(ibid). Two papers reveal that statement is not an up-to-date observation either (Antarctic floods, Greenland floods).
|Dr. Zwally had this upside down|
Among other things, Dr. Rignot provides graphs made from historical records, including satellite records from the very beginning of the Antarctica exploration.
The data are used to show clearly and convincingly how ice mass loss exceeds snow fall mass increase over long periods of time, as well as intermittently over short periods of time.
He also points out that mistakes (such as Zwally's) are typically made by selecting too short of a time frame (e.g. typical denier inordinate cherry picking of segments of records) from which to gather data:
27:17 Totten glacier area (a S.E. Antarctica drainage basin) alone has the potential to generate as much SLR / SLF as all of W. Antarctica(Dr. Rignot, paraphrased).
27:35 ice-mass loss Antarctica (segment begins)
28:00 the ice mass loss pattern must be observed with data taken over a long period of time or it can completely fool you
Dr. Zwally, get out of the past, and while you are at it lose the stubbornness too, or I am telling Dr. Zbeaver that you are full of it.
Previous post of this type is here.
"Ice streams are not like ice cubes." - Rignot
"They didn't have a clue." -Mitrovica