Saturday, June 13, 2015

The Surge: A Forgotten Aspect of Sea Level Rise

Surgical SLR
I. Preface

Over the past decades, sea level rise (SLR) has been seen as a regularly unfolding dynamic.

It has been perceived as being an experience like filling a backyard pool with the garden hose.

You turn the water on then observe a steady rate of increasing water level, until the spigot is turned off, and the rise in the water level stops.

Uniform, consistent. and linear is the perception of its rise to the desired level.

Scientific SLR models have been constructed with this same basic premise.

That is why they have consistently been wrong.

They have consistently underestimated reality.


Consider aggregation, echo chamber dynamics, and fear induced reticence (The Epistemology of Goldilocks RE: Sea Level Rise, An empirical examination of echo chambers in US climate policy networks, Scientific Reticence and Sea Level Rise).

II. The Observance of Surges in SLR

Lately, several Dredd Blog System posts have been concerned with the 1m / 3ft quantity of SLR.

That amount is generally considered to be a catastrophic event in today's configuration of civilization, because of the extensive use of ports, and the large populations along coasts (Will This Float Your Boat - 10).

It is specifically considered to be catastrophic along the East Coast from Cape Cod down to Cape Hatteras, because there has already been an SLR of about half that amount in that area (The 1% May Face The Wrath of Sea Level Rise First).

Additionally, there have been observations of surges in SLR there:
Coastal sea levels along continental margins often show significant year-to-year upward and downward fluctuations. These fluctuations are superimposed on a longer term upward trend associated with the rise in global mean sea level, with global mean sea level rising at roughly 3 mm per year during the recent 20 years of accurate satellite measures. For society, it is the regional changes along any particular coastal zone that are most important. Our analysis of multi-decadal tide gauge records along the North American east coast identified an extreme sea-level rise event during 2009–2010. Within this relatively brief two-year period, coastal sea level north of New York City jumped by up to 128 mm [5.05 inches]. This magnitude of inter-annual sea level rise is unprecedented in the tide gauge records, with statistical methods suggesting that it was a 1-in-850 year event.
(Will This Float Your Boat - 5, quoting NOAA). Historically, possibly because there was no civilization or coastal population like there is today, a 1m / 3ft SLR is considered relatively minor:
However, meltwater pulse 1C (8,200-7,600 years ago) left traces at numerous locations in the United States, northwestern Europe, and China. It occurred soon after the 8200 year cold event, which resulted from the final catastrophic drainage of glacial Lakes Agassiz and Ojibway around 8400 years ago. The torrent of around 100,000 cubic kilometers unleashed within a few years or less amounted to barely a meter rise in global sea level, if evenly spread across the world's oceans (note 1). Yet the stratigraphic record preserves vestiges of this relatively minor pulse.
(NASA GISS, emphasis added; cf. here). We can say that before the United States existed, surges of SLR of 1m / 3ft have taken place here, even leaving evidence of their existence in the geological record.

III. Surge "Climate" Is With Us Right Now

As noted above, SLR surges are taking place now on the North East Coast, and SLR surges have taken place there in the geographical area now called the U.S.A.

It has happened in the not very distant past (geologically speaking).

Yes, as the NASA GISS quote above points out, SLR surges have taken place "recently."

That "recently" is about 8,000 years ago, after the beginnings of human civilization ("The Anthropocene") had already taken place (e.g. Göbekli Tepe).

That surge was of course not linked to anthropogenic global warming induced climate change as surges in temperatures are now:
Anthropogenically driven climate changes, which are expected to impact human and natural systems, are often expressed in terms of global-mean temperature. The rate of climate change over multi-decadal scales is also important, with faster rates of change resulting in less time for human and natural systems to adapt. We find that present trends in greenhouse-gas and aerosol emissions are now moving the Earth system into a regime in terms of multi-decadal rates of change that are unprecedented for at least the past 1,000 years. The rate of global-mean temperature increase in the CMIP5 (ref. 3) archive over 40-year periods increases to 0.25 ± 0.05 °C (1σ) per decade by 2020, an average greater than peak rates of change during the previous one to two millennia. Regional rates of change in Europe, North America and the Arctic are higher than the global average. Research on the impacts of such near-term rates of change is urgently needed.
(Nature Climate Change, emphasis added). The East Coast of the U.S. is in the scope or sights of abrupt SLR surges ("... meltwater pulse 1C ... left traces at numerous locations in the United States" - ibid, NASA GISS, Section II, above).

Surges now are being caused by the same events that have caused them in the past:
Due to meltwater, lakes form atop the ice sheet in the summer – scientists call them “supraglacial lakes” — and they can grow to be quite large. And in July 2006, one large lake, over 2 square miles in area, suddenly vanished. It lost most of its water in under two hours – researchers calculated that the rate of drainage “exceeded the average flow rate over Niagara Falls.”
"Water-driven fracture propagation beneath supraglacial lakes rapidly transports large volumes of surface meltwater to the base of the Greenland Ice Sheet. These drainage events drive transient ice-sheet acceleration and establish conduits for additional surface-to-bed meltwater transport for the remainder of the melt season. Although it is well established that cracks must remain water-filled to propagate to the bed the precise mechanisms that initiate hydro-fracture events beneath lakes are unknown. Here we show that, for a lake on the western Greenland Ice Sheet,
The vanishing lakes mystery solved?
drainage events are preceded by a 6–12 hour period of ice-sheet uplift and/or enhanced basal slip. Our observations from a dense Global Positioning System (GPS) network allow us to determine the distribution of meltwater at the ice-sheet bed before, during, and after three rapid drainages in 2011–2013, each of which generates tensile stresses that promote hydro-fracture beneath the lake. We hypothesize that these precursors are associated with the introduction of meltwater to the bed through neighbouring moulin systems (vertical conduits connecting the surface and base of the ice sheet). Our results imply that as lakes form in less crevassed, interior regions of the ice sheet, where water at the bed is currently less pervasive, the creation of new surface-to-bed conduits caused by lake-draining hydro-fractures may be limited."
(The Question Is: How Much Acceleration Is Involved In SLR - 6?). Reviewing the quote about a 1m / 3ft surge ("which resulted from the final catastrophic drainage of glacial Lakes").

Ice melt produced lakes that grew large and suddenly emptied.

We see, then, that the same conditions exist now.

Again: existing conditions now are just like those back then which caused a surge of 1m / 3f of SLR. "within a few years or less."

IV. What Is Different Between Then and Now?

Back then, a 1m / 3ft SLR was considered to be a "relatively minor pulse" for that time, but the same surge now would be a serious catastrophe (Greenland & Antarctica Invade The United States).

Nevertheless, the current warming climate conditions are expected to accelerate absent a proper response from current civilization.

A smug mood has blinded officials to the clear and present danger (Oil-Qaeda & MOMCOM Conspire To Commit Depraved-Heart Murder).

The large coastal populations now, as well as the dependency on international trade via sea ports, means that the difference, in terms of loss of life and infrastructure, couldn't be more pronounced.

V. Conclusion

The beginning of a sudden SLR, which would reach a level of 1m / 3ft, could take place at any time, because the conditions for an SLR surge already exist right now.

It would reach catastrophic levels "within a few years or less" if it follows the pattern of events that took place about 7,000-8,000 years ago.

The laws of physics have not changed in that relatively short span of time.

The myth about it taking centuries, or decade upon decade, should be discarded (Why Sea Level Rise May Be The Greatest Threat To Civilization - 3).

We really do not have plenty of time, all we have is daily exposure to a roll of the dice, and a possibility of failing The Test (The Tenets of Ecocosmology).

A surge @ Totten Glacier area is a new problem:


Randy said...

Agnotology studies show that ignorance about the Arctic is most predominant in the political party of Senator Inhofe (link, link).

Dredd said...

“There was nothing happening, and then, all of a sudden in the last five years, all of these glaciers started to send ice into the ocean,” says Bert Wouters, a glaciologist at the University of Bristol, UK, and an author of the study. - Nature - W.Antarctic Surge)