The Rare Supermoon that dominated the skyline, has been a hot topic in this week's news.
The rare supermoon which dominated the skyline for many, presented a natural wonder for many stargazers, however, there are devastating side effects related to this lunar event which has seen high tides and flooding in parts of America.
Last Mondays supermoon meant that the moon has been the closest to the Earth, than it has been in nearly 70 years. A supermoon happens when the full moon coincides with the lunar orb's closest approach to Earth during its orbit. The full lunar dusk appeared 14% bigger and 30% brighter than usual. One of the effects of the supermoon is stronger high tides due to the increase gravitational pull.
Miami, as well as many other areas, saw heavy coastal flooding. The supermoon increased the effect of the seasonal king tides- the highest predicted high tide of the year at a coastal location, which occurs once or twice a year- caused low lying areas to be immersed in water.
According to the New York Times:
"These so-called king tides, are the most blatant example of the interplay between rising seas and the alignment of the moon, sun and Earth. Even without a drop of rain, some places flood routinely".
Rising Sea Levels
Coastal areas prone to flooding see higher tides monthly due to spring and proxigean tides. When they occur together the impacts are worse, but not catastrophic. If you were to add a third force for example a storm, things can deteriorate very quickly, creating storm surges and inundating low low lying areas.
Now add sea level rise into the picture. One of the main causes of coastal flooding is the rise of sea levels. Sea Level rise is caused primarily by two factors related to global warming (1) melting land ice at the poles; and (2) thermal expansion of seawater as the oceans warm. Tide gauge measurements has shown that sea level has risen by an average of 1.7 ± 0.3mm/ year since the 1950s. However, sea level rise has accelerated especially since the 1990s (Nicholls, 2010) causing the sea levels to rise by 3.4± 0.4mm per year. Since 1993 it has risen 85mm (figure 1).
Figure 1: Global sea level rise 1993-2016
Modelling studies (figure 2) have shown that by 2100 sea level rise will range from 0.57 to 1.10m, with the maximum rate of sea level rise reaching 17mm/year according to the RCP8.5 pathway (Jevrejeva, 2012).
Figure 2: Sea level projections 2100 with RCP scenarios
Risk
'At the UN COP21 climate change summit in Paris December 2015, a target was set to limit global temperature rise to below 2℃'. May 2016, Christian aid released a report 'Act now pay later: protecting a billion people in climate- threatened coastal cities'. They detailed how by 2060 more than 1 billion people will be at risk from rising seas, flooding, extreme weather and storm surges caused by climate change.
The US who is one of the biggest emitters of GHGS, is likely to suffer most from coastal climate change, due to the value of exposed property, business, investment and other assets.
Miami
The coastal city this week hit headlines due to flooding. With 4.7 million residents, it is the top 9th city at risk in terms of population, but tops the list in financial terms, with > US$3.5 trillion worth of assets predicted to be exposed to extreme weather and flooding by 2070. Below shows a map (figure 3) of the areas that would be underwater in Miami if sea levels rose by 6 foot, that is 32,986 homes.
Figure 3: Underwater homes in Miami
The flood this week, is just one of many issues the Miami area has faced because of rising sea levels. A university of Miami study published earlier this year found that flooding from rising tides has increased 400% since 2006. They also found that rising sea levels increased the frequency of rain- induced flooding events by 33%, because the higher sea levels reduced the effectiveness of gravity- based drainage systems.
Thus in 2014, the city of Miami beach invested at least US$400 million in replacing old gravity based drainage systems with a new pumped-based systems throughout the most flood- prone areas. They are also investing into raising street heights.
Concluding thoughts
The flood this week was not necessarily directly caused by climate change, however sea level rise due to warmer temperatures has increased the magnitude of it.
Flooding in Miami is highly predictable, this low-lying area is already prone to flooding, especially due to monthly high tides, its porous limestone geology, and ineffective drainage systems. Therefore, it is not to say that sea level rise is causing flooding, because that is not the case. But climate change has meant that this area has become more susceptible to flooding- 'When it rains it floods', and there is simply more flooding. And this will get worse.
Climate change here is no longer seen as a future threat, and an expensive one it is. Is this a glimpse into the future for the rest of the world?
Flooding in Miami is highly predictable, this low-lying area is already prone to flooding, especially due to monthly high tides, its porous limestone geology, and ineffective drainage systems. Therefore, it is not to say that sea level rise is causing flooding, because that is not the case. But climate change has meant that this area has become more susceptible to flooding- 'When it rains it floods', and there is simply more flooding. And this will get worse.
Climate change here is no longer seen as a future threat, and an expensive one it is. Is this a glimpse into the future for the rest of the world?
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