Is A New Age Of Pressure Upon Us? - 6

Active Volcanoes Under Polar Ice Sheets

In this series we have been discussing the pressure changes on the Earth's crust that melting ice sheets have induced in the past, are now inducing, and will be inducing in the future.

Especially interesting is sensitive crustal areas we can call "hair-trigger zones."

Those are areas such as earthquake fault zones, areas where volcanoes have been impacted by thinning ice sheets over them, and the general torque across the whole crust under the oceans.

These pressures come from weight removal as ice caps become thin, then from weight increases on the crust as the sea level rises (e.g. Is A New Age Of Pressure Upon Us? - 5).

A new study conducted in the Southern Hemisphere indicates that volcanic activity under the Thwaites Glacier in Western Antarctica may be increasing:

Thwaites Glacier is one of the West Antarctica’s most prominent, rapidly evolving, and potentially unstable contributors to global sea level rise. Uncertainty in the amount and spatial pattern of geothermal flux and melting beneath this glacier is a major limitation in predicting its future behavior and sea level contribution. In this paper, a combination of radar sounding and subglacial water routing is used to show that large areas at the base of Thwaites Glacier are actively melting in response to geothermal flux consistent with rift-associated magma migration and volcanism. This supports the hypothesis that heterogeneous geothermal flux and local magmatic processes could be critical factors in determining the future behavior of the West Antarctic Ice Sheet.

(New Study - Volcanic Activity). This type of activity was not only predicted by scientists, it has already happened exactly as predicted under ice sheets in the Northern Hemisphere:

In August of 2007, over 2.5 years ago, a geologist had studied the historical record for global warming events which were not anthropogenic (not caused by human activity).

His conclusions were that global warming has caused volcanic eruptions and earthquakes in the ancient past.

He went on to say that the anthropogenic global warming occurring now will do so too.

Over two and a half years ago he mentioned by name the very volcano that just erupted in Iceland shutting down air traffic over Europe.

He also indicated that earthquakes could result from anthropogenic global warming:

"In places like Iceland, for example, where you have the Eyjafjallajökull ice sheet, which wouldn't survive [global warming], and you've got lots of volcanoes under that, the unloading effect can trigger eruptions," McGuire said.

With the changing dynamics in the crust, faults could also be destabilized, which could bring a whole host of other problems.

"It's not just the volcanoes. Obviously if you load and unload active faults, then you're liable to trigger earthquakes," McGuire told LiveScience, noting that there is ample evidence for this association in past climate change events.

(Live Science, 2007, emphasis added) ...

(Global Warming & Volcanic Eruptions). Remember that we are talking about pressure-change activity having a more noticeable impact where there are triggers in sensitive areas of the crust:

Our results suggest that long-term and late-summer flexural uplift of the Coast Ranges reduce the effective normal stress resolved on the San Andreas Fault. This process brings the fault closer to failure, thereby providing a viable mechanism for observed seasonality in microseismicity at Parkfield and potentially affecting long-term seismicity rates for fault systems adjacent to the valley. We also infer that the observed contemporary uplift of the southern Sierra Nevada previously attributed to tectonic or mantle-derived forces is partly a consequence of human-caused groundwater depletion.

(Is A New Age Of Pressure Upon Us? - 5). Thus, even a drought can become serious enough in a sensitive trigger zone to stimulate events that otherwise are not likely to take place ["Scientists at Scripps Institution of Oceanography at UC San Diego have now discovered that the growing, broad-scale loss of water is causing the entire western U.S. to rise up like an uncoiled spring." - Phys org].

Note also that some of these pressure changing events are one form of what is called "a feedback loop" ... such as:

One of the more amazing facts about the ongoing destruction of the Greenland ice sheet is that it is producing earthquakes that can be detected worldwide. Now, fresh evidence is at hand to show that these “ice quakes” are spreading to previously quiescent parts of Greenland. We’re only in September, but it seems increasingly likely that 2012 will set a record for such quakes.

(Is A New Age Of Pressure Upon Us? - 4). Feedback loops happen when anthropogenic global warming triggers events that cause an additional surprise increase in global warming or increase in direct damage (e.g. methane release from the melting Arctic permafrost is another type of feedback loop).

The greatest danger some of these feedback loops pose is that they can lead to tipping points being reached sooner than they otherwise would have.

Once tipping points kick in we can't stop them no matter how quickly we then decrease our fossil fuel use in response.

The point, then, is to diminish fossil fuel usage and switch to renewable fuels before we trigger those tipping points, not afterwards.

The next post in this series is here, the previous post in this series is here.