The Culprits of the Rift (WEEK 4)

The first part of this project explores the how: how is the loose tooth fork rift on the Amery Ice Shelf changing over time? This is a question that I have outlined throughout the past three blog posts. Now, however, it is time to turn to the second part of this project – the why: why is the loose tooth fork rift experiencing the changes we have observed?

 

This is an incredibly difficult question to answer. The reason it is so difficult is because the Earth’s climate system includes countless mechanisms, variables, and components that influence countless other mechanisms, variables, and components in countless ways. The graphic below, for example, portrays the complexity of the Earth’s climate system quite well.

Climate interactions diagram

While it is possible that any of the internal components of the climate system could impact the AIS rift, I will only examine forcings that I suspect relate most directly to the rift propagation.

 

Climate-Change Related

As discussed in the original blog post, there has been a net loss of Antarctic ice due to climate change. And since some methods of ice loss begin with rift propagation, it is entirely possible that the changes we are seeing on the Amery Ice Shelf are due to climate change. The graphic below shows several potential surrounding threats to the AIS’s stability.

Ice sheet dynamics pic

Forcings from Above: Atmospheric Temperatures

One way that ice is weakened is through warming temperatures. As such, it is possible that warmer overlying air temperatures correlate with quicker rift propagation and/or advance.

Forcings from Below: Ocean Temperatures

While all of the satellite images display the Amery Ice Shelf from above, it is important to note that ice zshelves, by definition, float on water, rather than being directly above land. In fact, due to buoyancy properties of ice and differences in density between frozen and liquid ice, approximately 90% of the Amery Ice Shelf is submerged in the underlying Arctic Ocean. Furthermore, it is possible that the loose tooth fork rift started to propagate from the bottom of the ice shelf, and then make its way to the stop so as to be captured in satellite imagery. Thus, it is possible that warmer underlying ocean temperatures correlate with quicker rift propagation and/or advance.

Forcings from the Sea: SIC, Tides, & Winds

It is entirely possible that the strength of the ice shelf could also be influenced by the surrounding sea. For example, when there is a large amount of sea ice surrounding the Amery Ice Shelf, then there is more of a barrier to wave energy from reaching the ice shelf, and as such, the ice could be stronger and less susceptible to rift propagation. Thus, I would expect a lower rate of rift propagation in the winter than in the summer.

Some additional sea-influenced forcings could include tidal and/or wind energy, but those are likely potential forcings that I will not be investigating in this research project.

 

Non-Climate-Change Related

To further complicate investigating the whys behind the rift propagation that I have observed and measured thus far, it is also possible that the rift propagation is not related to climate change. Here are two possible alternate explanations.

Tectonic activity

Some research papers I read before I began data collection suggest that there is a possibility of “icequakes”, or tectonic activity that’s fault line closely mimics that of the rift. This could be a predominant force behind the rift propagation rates.

No “special” forcing

Throughout the past two decades, the AIS rift might have been propagating at roughly the same rate as they normally would, regardless of whether man-made global warming existed. While I would generally doubt this because of climate change’s incredibly wide-reaching impacts, this possibility cannot be ruled out.

 

Lag Time

To yet again further complicate matters beyond just pinpointing (a) possible forcing(s), it is also important to consider the concept of lag time. This is the amount of time between when a cause occurs, and when its effects become apparent. For example, if a month of above-average temperature burst correlated with quicker rift lengthening, then it is likely that the quicker rift lengthening would not appear until days, weeks, months, or even years after the above-average temperature burst.

 

I will spend the rest of the summer compiling data sets of ocean temperatures, atmospheric temperatures, and surrounding sea ice concentrations in an attempt to correlate them with the rift propagation and alterations I have measured.

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