by Daniel Brouse
Seismic Climate Events: When Cryosphere Instability Becomes an Earth-System Hazard
I’ve written quite a bit about “Sudden Sea Level Pulses: How ‘Cork Release’ Events Could Rapidly Reshape Coastlines,” which you might find interesting. I expect we will see several feet of sea-level rise for several years in a row this century.
The big examples in Earth’s past occurred when proglacial lakes suddenly broke through ice dams during the last deglaciation.
When the last Ice Age ended, the Earth experienced “Meltwater Pulse 1A”—a dramatic period roughly 14,500 years ago when sea levels surged upward by about 66 feet in just 500 years. Data from Barbados, Tahiti, and Sunda confirm that the ocean rose at astonishing rates—sometimes more than 40 mm per year. We should expect similar patterns again.
I find sea-level rise very intriguing. However, the problem has always been that it is too “slow” for anybody to care. What’s a couple of millimeters a year?
It took us 10 years to confirm that sea-level rise was doubling every ~100 years—2²-fold on a centennial basis. Since the late 1990s, that doubling time has collapsed to 3–10 years. The collapsing doubling times indicate that SLR acceleration is accelerating at approximately 2⁶-fold on a decadal basis.
Though this jerk/third-derivative behavior is alarming to me, it still doesn’t seem to get people’s attention. This is just one set of climate-impact datasets. Many others show the same rate of acceleration.
Now, we’re crossing 1.5°C in a hurry.
This is where jerk behavior will get people’s attention.
We are fairly confident there are several feet or more of dammed-up meltwater. Jerk behavior puts a much higher probability on jerk-like reactions.
The result isn’t going to be a meter of sea-level rise overnight. It is much more likely to be a serious breach in Greenland that raises sea levels perhaps a foot the first year, two feet the next year, and another foot the following year. Then it may go back to millimeters or inches a year for a few years.
This is one of those feedbacks that is very difficult to comprehend.
Greenland has a lot of dammed-up meltwater. Greenland’s geology is shaped like a bowl. If the ice were to melt in place, most of it would likely stay in the bowl.
But hold on—not so fast.
Sudden-release events on Greenland are not the same thing as slowly melting ice over the last 40 years.
When the geology gives way, as it did in 2023’s Dickson Fjord seiche, the consequences can be extraordinary. That massive rock-and-ice avalanche, involving approximately 25 million cubic meters of material, created a tsunami that registered worldwide as an earthquake for nine days.
Recently, in Nepal–Tibet, a similar incident produced seismic waves equivalent to those generated by a magnitude 4.4–5.2 earthquake.
It is an example of what can be described as a seismic climate event: climate-driven changes in glaciers, permafrost, snow, and mountain stability can increase the potential for enormous mass movements, which in turn release sufficient mechanical energy to generate measurable seismic signals.
The broader danger is the cascade.
Warming can destabilize the cryosphere. Cryospheric destabilization can trigger massive avalanches and landslides. Those failures can block rivers, generate flash floods and debris flows, and even produce detectable seismic waves.
The resulting disaster is therefore not the product of a single hazard, but of multiple interconnected Earth-system processes interacting in rapid succession.
Greenland gets even more interesting.
That bowl-like shape was caused by the weight of the glacier. As the glacier and meltwater quake into the sea, there will be fairly rapid rebound, and the bowl bottom will rise back up. This rebound is already much faster than earlier predictions.
This all brings Antarctica into the picture, potentially coupling with Greenland. That could be really drastic compared with Greenland alone.
In particular, Sidd said:
“Yes, I saw that. Under-ice hydrology is hard to observe, but there have been efforts with maps made of Greenland and Antarctica—probably incomplete. I still think Greenland will melt largely in place; Antarctica is the big one.”
See: Greenland Melting Is Inevitable
So how much faster the new-normal sea-level rise will be after such an event is quite uncertain—as is how long it will be until the next sudden release.
The important point is that climate change does not necessarily operate as a smooth, linear progression.
Sometimes the Earth system stores energy and mass until a threshold is crossed. Then the response can become abrupt. This is an observable tipping-point cascade, where one threshold crossing can destabilize another system and trigger a rapid sequence of interconnected changes.
That is the fundamental concern with seismic climate events: the climate system is increasingly interacting with a destabilizing cryosphere and a mechanically active landscape, creating the potential for cascading events that are far faster than the gradual changes that initially caused them.
