Antarctica's Mass Gains Put in Perspective
(Originally posted February 15, 2017 on Blogger)
If Earth is experiencing accelerated global warming, then how is it possible that Antarctica is actually gaining ice mass, not losing it?
In October of 2015 NASA published a paper in the Journal of Glaciology that describes a net ice mass gain on Antarctica. In the time since its publication, there has been a considerable amount of confusion for those of us not directly involved in this research. How can there be ice accumulating in Antarctica when we're told the ice caps are melting, and global warming is running rampant?
Here is a link to the actual paper for those interested:
Mass gains of the Antarctic ice sheet exceed losses
H. Jay ZWALLY et al., Journal of Glaciology, Vol. 61, No. 230, 2015 doi: 10.3189/2015JoG15J071
The paper's title and abstract have led many to believe we have nothing to worry about with regard to global climate change.
Unfortunately, most people are unaware that papers like the one above are freely available, if not directly from a home computer, then from a public library. Worse still is that many curious minds rely on social and/or mainstream media to interpret the papers for them.
More often than not, this sort of reliance is met with inaccurate, and/or partial interpretations that--whether intentional or not--mislead well-intentioned people who may not have the time to interpret the oft-complicated data and lingo prevalent in peer-reviewed publications.
Take for instance this interpretation of the 2015 paper (links to a media outlet's interpretation of the paper):
The above article correctly states what the 2015 paper concludes; that Antarctica is gaining ice mass and--based off current estimates--is expected to continue this mass gain for up to thirty years to come. The message comes off ad hoc, but indeed states facts given in the paper.
The problem with this, and other articles conveying the same general message, is that they are pandering partial-truths. Partial truths are deceptive by nature, and difficult to expose as such given the fact they contain some element of truth. They tend to be partly true, totally true but only insofar as that part of the whole truth they give, or they use deceptive linguistic elements such as improper punctuation, double meanings, and inject any number of logical fallacies; the straw man fallacy being one of them. I knew someone who was quite adept at this sort of thing.
With regard to ad hoc argumentation, we can take my blogs on Mars as example; I know someone else who disagrees with me on my points, but aside from ad hoc single-sentence remarks and Elon Musk regurgitations, they have yet to counter my points with logical or at least arguable points of their own.
This sort of thing happens to us all from time-to-time. The important thing is that we know all the facts we can gather about anything we find to be important, then proceed with tentative mindsets so that we can be open and accepting should new and different facts challenge our previous conclusions.
This is the nature of science afterall. This, coupled with an awareness of the most common logical fallacies, will ensure we maintain a purely scientific perspective on things that ought not be sociopolitically charged.
With that said, let me preface my explanation of the 2015 paper by stating clearly that it will conclude within a global context. For simplification, I will only consider continental glacial ice, because meltwater from continental glaciers contribute to sea level rise, whereas sea ice meltwater does not.
This isn't to say that thermal expansion of seawater does not contribute to sea level rise; it most certainly does, and likely contributes to half of that rise. But to avoid an overly-long blog (those tend to have the fewest views!), I'll keep this as direct as possible. Besides, if my blog ends up being longer than the paper it means to clarify, then I probably need to go back and better understand the paper!
THE NITTY GRITTY
Antarctica hosts the largest single mass of ice on Earth, covering 5.4 million square miles with 6.4 cubic miles of ice. These are incomprehensible scales outside of numbers on a page. With growing concerns of global climate change, scientists from NASA and the ESA worked to send monitoring satellites into polar orbits to measure for any ice gains or losses from the Antarctic continent.
Three satellites were used to measure ice mass gains/losses across Antarctica. Two European Space Agency (ESA) satellites; the European Remote Sensing satellites ERS-1, and ERS-2 were placed into Sun-synchronous polar orbits. They operated from 1992-2001, during which time they recorded and calculated ice mass measurements utilizing sophisticated on-board radar altimeters. The third satellite was NASA's Ice Cloud and land Elevation Satellite (ICESat) that also measured ice mass gains/losses over time (2003-2008).
The ERS duo recorded ice mass gains of 112 gigatons/year (Gt a-1), give or take 61 Gt a-1. This coincides with results from NASA's ICESat that calculated ice mass gains of 82 Gt a–1, give or take 25 Gt a-1. This net gain in ice mass has been ongoing since the early Holocene over 11,000 years ago when the planet (as a system) began coming out of the Last Glacial Period ("Ice Age").
With temperatures on the rise, warmer air currents have since been able to transport more water vapor across Antarctica, as much doubling the amount of snowfall upon the continent as compared to what fell during the last Ice Age. Research scientists were able to conclude pre- and historic annual snowfall rates based off ice core samples taken from across Antarctica's ice sheet. About 1.7 cm/yr of ice has accumulated upon existing ice ever since.
Many of us have heard the narrative that it shouldn't surprise anyone that the planet is warming given the fact that we've been coming out of an ice age for millennia. It is true, we have been coming out of The Last Glacial Period, itself one of a series of 'ice ages' that are part of the on-going Quaternary Glaciation we're currently in and that Earth has been experiencing for the past 2.58 million years. The planet will experience more ice ages. I will write a blog on Quaternary Glaciation and the concept of deep time in the next blog. I'll be sure to include how holding out for an ice age that is anywhere from 15,000 to 50,000 years from now is probably not a good basket to put our eggs in. For now, it's important to know we are in an interglacial event (warming period). As such, it goes without saying that natural warming trends and their effects have and will occur.
But just as I mentioned earlier about partial truths, it is more important to understand that the rate of this interglacial warming trend has increased dramatically in recent decades. Warming includes both that which occurs over time within the troposphere as well as the upper ~30 meters of the world ocean (it's really just one big ocean).
In fact, the world ocean 'absorbs' up to 90% of heat radiation, effectively sparing the troposphere from the full extent of additional greenhouse gas infrared emission. So when scientists see sea level rise as a result of thermal expansion and continental glacier meltwater--while understanding the physics of energy transfer--they become rightfully alarmed.
No scientist on Earth has quantified exactly where certain thresholds exist beyond which positive feedback would occur. Given that fact, any statistically significant rate changes in otherwise natural global energy transfer processes should be taken seriously. It's analogous to walking towards a cliff blindfolded. You know it's there, but you don't know how far. Each step you take, therefore, is taken with evermore consideration... to put it lightly.
One might think that the 2015 paper comes as a relief; mass gains of the Antarctic ice sheet exceed losses. However, the paper makes it clear this net gain is being chipped away at a rate that will result in a net loss for the first time in 11,000 years by the 2040s.
To folks like 29-year-old Steven Crowder (see link above to his article), 30 years must seem like a lifetime! And to him, it literally is. However, on a geologic time scale, 30 years is no time at all. Many of us (Mr. Crowder included) will be alive to witness the planet's single largest ice sheet begin to decrease in size. The effects of which are quite alarming to consider.
CONSIDERING THE EVENTUAL NET LOSS
As of now, Antarctica's net gain (contrary to what the IPCC report says), removes ~0.23 mm from global average sea level per year. However, despite this removal, sea level continues to rise at a rate of ~0.27 mm per year. The fact global sea level is rising on average should be disconcerting, particularly when it is rising even though Antarctica is acting to lower it. What's more disturbing is that in 20 to 30 years, Antarctica will begin using its unparalleled mass to contribute to sea level rise. The single largest mass of ice on the planet will go from removing water from the global ocean, to adding to it.
The 2015 paper describes that the net gain has slowed from 112 billion tons of ice per year from 1992-2001, to 82 billion tons per year from 2003-2008. (Data ends in '08 because that was the end of the ICESata mission. A new satellite, ICESat-2 is scheduled for launch in 2018, and I suspect the rate of mass gain will have decreased further; if so, then it suggests (to me) that a threshold has already been crossed.) That is 30 billion tons less effective at buffering against sea level rise.
The decrease is largely attributed to increased discharge (meltwater) rates out of west coastal Antarctica and the Antarctic Peninsula. It is the discharge rate increases from these drainage systems (AP, WA1, & WA2...see image below) that are fast diminishing the continent's net mass gain.
THE GLOBAL CONTEXT
Though Antarctica is the largest single mass of ice on Earth, it isn't the only one. There is another; the Greenland ice sheet. The Greenland ice sheet is the second largest mass of ice on the planet after Antarctica, and it is experiencing a net loss of ice that exceeds the net gain of Antarctica. In other words, the planet is experiencing a global net LOSS of ice.
Greenland experienced an annual ice mass loss rate of 96 cubic kilometers in 1996. This rate of loss INCREASED to 220 cubic kilometers by 2005 (source: http://www.jpl.nasa.gov/news/news.php?release=2006-023).
If we subtract that from the average gain of over Antarctica (let's say an average of 97 Gt a-1), then we end up with a net loss of 32.5 trillion gallons of discharge into the world ocean per year. That's with Antarctica taking up water, not contributing to it. A buffer the paper clearly states will not last more than 2 or 3 decades. An estimate that may decrease further once the new ICESat-2 enters orbit and begins sending data back.
To put 32.5 trillion gallons in perspective--for those who have read my blogs on California's water system--that's over 10 trillion more gallons of water than the State Water Project (SWP) has delivered to all 29 contractors since its inception in 1960.
To put the number one-trillion into perspective, consider that a million seconds equates to about 11 days, a billion seconds is almost 32 years, a trillion seconds is over 31,700 years.
I hope this blog shows how a partial truths have and never will tell the whole picture. They're not supposed to. That's their point. But that's not how science works.
As always, thanks for reading.
UPDATE: February 15, 2017
Ice loss from Canada's Arctic glaciers has transformed them into a major contributor to sea level change, new research by University of California, Irvine glaciologists has found.
Source: Romain Millan, Jeremie Mouginot, Eric Rignot. Mass budget of the glaciers and ice caps of the Queen Elizabeth Islands, Canada, from 1991 to 2015. Environmental Research Letters, 2017; 12 (2): 024016 DOI: 10.1088/1748-9326/aa5b04