Daily Archives: April 15, 2013

Mapping Holes over Poles: Disappearing Stratospheric Ozone

Maps can make wonderful arguments to orient us to a variety of global processes whose scale could not otherwise by visualized or even adequately comprehended.  Maps of the relative size of the depletion of ozone over Antarctica over time, looking at the earth’s atmosphere from the South pole and mapping the threat of a monumental environmental shift to allow us to consider changes in the loss of stratospheric ozone that have recently occurred, in ways that are only adequately understood by few:  diachronic maps provide the best means to chart the emergence at the poles, due to the similar pocket of cold air, of the disappearance of the thin layer of ozone that encloses the earth’s atmosphere, and blocks 90% of UV rays of solar radiation:

Sept 2006-Sept 2012 ozone

These two maps centered on Antarctica highlight where weather conditions helped expand the largest ozone “hole” in the stratosphere–a region where ozone has been reduced from 300 to 100 Dobson units, or by two-thirds, and an unprecedented entrance way for UV radiation unveiled.  With the continent of Antarctica reduced to an exposed island in the bright green iris of a protective level of stratospheric ozone, they map provides both a visualization of the permanent gap through which UV radiation enters our atmosphere, and the stubborness with which a problem that first registered at the British Antarctic Research station in 1985, literally wasn’t accepted as genuine, so sudden and unthinkable was its appearance:  deep blue registers the diminution of high-level ozone to 220 Dobson Units, the lowest ever recorded up to 1979.

There’s a tension in using bright iridescent hues to represent a tenuous layer that, if not so widely dispersed, would be only just three cm. in width.  The fragility of this protective if thinly distributed layer may be impossible to visualize as a unit, and as difficult to map as the mechanics of its depletion is to grasp or predict.  The depletion of ozone in the “hole” –more of a relative absence of ozone that usually checks UV rays–lacks the sort of boundaries or objective parameters maps chart, and its gradations hard to ascertain from the ground:  the tenuousness of the dispersed level of ozone in other words challenges cartographical denotation; exactly how much radiation enters the earth’s atmosphere is harder to calculate or represent, so we are left with registering the diminution as an effective ‘hole,’ given the lack of objective criteria to map the diminution in spatial terms that narrate the scope of its effects.  Such obstacles or constraints in mapping has no doubt lead to well-warranted criticism of inadequate appreciation of its seriousness or persistence in media stories that champion its reduced relative size, as we try to grasp  a process we can’t control.  This seems tied to the difficulty of presenting an argument in recognizable graphic conventions, and the appropriation of the map above as an argument that the hole’s expansion reduced and is under control or no longer subject to further expansion.

The inability to map a relationship between the hole and the land in anything like a one-to-one fashion of meteorological maps creates a challenge in registering satellite readings of a thin layer spread across the upper reaches of the stratosphere as if it were an object or place.  The iridescent hues that render depletion of ozone map are both misleadingly and deceptively presented, Bruce Melton argues, as evidence of a “record low” ozone hole–since the reduction in size conceal the fragility of the tenuous ozone layer when increased stratospheric cooling will further deplete the failure of ozone, as Melton argues, and create an uphill struggle to ever block the entrance into our atmosphere of radioactive UV rays.  The map is in this case not the territory:  the territory is being irradiated, and is going to be irradiated for some time.  Climatologists predicted many narratives of the hole’s eventual shrinking in the early 1980s, or in 2006, when it was noted that “in Antarctica, we can say that the patient is not getting any sicker, either,” and 2006 led to the prediction tha reducing fluorocarbons would bring clear evidence of unambiguous improvement by 2016.

Yet the persistence of the hole is striking:  2011-12 saw the re-emergence of a similar ‘hole’ above the north pole, far closer to inhabited areas.

The evidence is difficult to interpret, and harder as a result to represent in maps.  Most maps effectively materialize or embody land and a relation to space, but the hole or gap records the depletion of a gas whose effects are far greater than its relative size, and not necessarily proportional to its size.  To be sure, after being warned of the eventual depletion of ozone, it does not seem so inevitable. Although naming a “hole” seems concrete–something is leaking or escaping from a delimited zone–the entrance of UV rays through this “hole” can’t be adequately mapped to reveal or represent what is happening climatically, and the scope of the dramatic increase of the ozone hole’s radius is difficult to imagine, for  it’s difficult to know what the size of the hole means.

The perspective above Antarctica shows an area about as large as the Antarctic continent itself to be entirely depleted of ozone.  This map of absence challenge us to chart something that resists most of the usual categories of maps.  Perhaps the process is better communicated by mapping the distribution of real-time ozone loss at an altitude of twenty kilometers, as the below visualization of the World Data Center for  Remote Sensing of the Atmosphere, using a vertically resolved distribution to  map variations in loss and depletion of ozone, showing a significant reduction above the north pole that becomes more urgent below the equator:




A similarly striking map of local variations from the normal density of 300 Dobson units, tells the difficult to grasp story of wide-ranging atmospheric shift over the southern hemisphere at a time of greatest ozone depletion, of which the hole over in the ozone layer over Antarctica is only a section:



Mapping the absence of ozone in the atmosphere is a difficult proposition as well as graphic, especially since most maps are static in nature. The first two visualizations of NASA’s Ozone Watch centered on the continent of Antarctica portray the region’s exposure to UV rays, as if one is somehow looking up the world’s skirts, in ways that work because they tweak or shake up the notion of a global map to show a vital or exposed place in the world’s atmosphere: the perspective from  from that of solar radiation entering our atmosphere suggests looking into something that one shouldn’t be able to see.

It’s a bit comforting that there was some contraction from the massively gaping hole of 2006,  but the slight apparent contraction doesn’t really offer any reassurances.  If purple and blue is where ozone is least present, and yellow toward the red end of the spectrum where it is most present, the hole is still gaping pretty large in April, 2013:  the ozone (O3) in the upper atmosphere is present in such trace amounts, that its absence from the stratospheric atmosphere allows ultraviolet radiation to seep in; while it can absorb the most dangerous and intense radiation before it reaches the earth’s surface, ozone depletion allows it to enter freely.

We can far more easily, of course, map the extent to which more and more ozone is itself trapped, as a greenhouse gas, in our atmosphere, but that is not where we want it–its benefits are nil and even adverse since it is a health hazard.  Its concentration as measured in our country roughly matches concentrations of smog:

National US Ozone Map

The above map registers ozone created from car and other industrial emissions lying below the stratosphere, and the rise of parts of ozone/billion from 10-15 in pre-industrial society to upwards of 80–a rise that has largely contributed to local smog or “ozone days,” and the “spare the air” days of the East Bay when folks are asked to take public transit.

The geographic centers of pollution documented from satellite photographs from 2006 to travel surprisingly wide distances, in ways that suggest we try to understand the local heights of ozone as a truly global crisis if it is also one of local creation:


This concentration of atmospheric ozone is a form of smog, that serves no protective function as a trapped greenhouse gas; the ozone layer in the stratosphere itself has little relation to global warming.  But we can perhaps develop a perspective of more global character to map or visualize the absence of ozone at stratospheric levels.

This was, after all, the primary effect when NASA compellingly created a map of the relative depletion of ozone concentration–and the potential disappearance of stratospheric ozone–from 1994 to 2060, should  further production of CFC’s not be banned.  This image of ecological disaster was not fleshed out, but is apparent in the deep blue hues that uniformly enveloped the familiar form of North America, as if to tell our future gone astray as a consequence of the increasing industrial production of fluorocarbons worldwide:



The mapping of more recent depletion of ozone over the pole is the consequence of its unique climate, mapped a sort of topography of ozone loss, in which blue and violet mark significant deviations in local ozone concentrations that were sensed in 2003, but were first detected as early as 1985:

And the resulting spottiness of the ‘ozone column’ prominent in this global map of 2006 suggest a broad depletion of ozone layers around the equatorial region, where the sunlight is also more unremitting and intense, outside of the polar regions:

Ozone Column 2006


What does this massive decline of a shield against radiation mean?  As of yesterday, the map was considerably expanded and not much more comforting, looking at online near real-time ozone maps:



NASA also continues to provide daily visualizations of the established gap in ozone over the Antarctic, based on satellite measurements, to register a daily changing picture of the hole that is not much more comforting:




Such snapshots tell half the story; stop-action photographic frames chart the hole’s growth form 1979 to 1991 shows the difficulty in pinpointing its size or shape, providing something of a narrative, as registered by satellite spectrometers:

The jerky seasonal variations seem to be always up for grabs! But a compilation of monthly averages in a suggestive sequence of time-lapse stills, also from Cambridge’s Centre for Atmospheric Science, reveals the expansion of the violet blotch almost appear from nowhere in about 1983, when it was first detected, in ways linked to how gasses emitted from CFC’s had dramatically depleted atmospheric ozone:


Cambridge Ozone Maps


These Cambridge Ozone Maps–a wonderful name–show an odd shifting of form, shifting due to polar meteorology, of how the gasses spewing out of factories, homes, and airplanes attach to stratospheric clouds that, in the polar vortex, introduce atomic chlorine over the pole which at such low temperatures, destroy ozone.

To map the loss of the layer over time, in animated form, is perhaps far more compelling than a static map is able to offer its viewer:

For the lack of better conventions to visualize the opening of ozone over the earth, its hard to remember the difficulty of turning back or reversing this depletion at all.  The challenges of mapping ozone are multiple, both because of the stories we impose on the maps and an inability to comprehend the costs of the opening hole hovering over the pole.  Is it that the map embodies a process that can be visually grasped, transforming a topic of debate into an entity that cannot be denied?  Indeed, there seems a relative poverty of words–what is a hole, actually?–that seems resolved when one looks at the maps of stratospheric ozone depletion over the poles, and sees where the ever-widening gap lies.

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Filed under Antarctica, global warming, Ozone Hole, Solar radiation, UV Radiation