Rising Sea Levels
As global warming continues, Earth is threatened by rising sea levels. But what does that exactly mean and where is it all coming from? And given how vast the oceans are, one would think that it would take a lot for it to really be problematic.
Over the course of the last century, global sea levels are rising. Currently, they are rising at a rate of about 1/8" per year. This rate will increase, however, as the leading cause of it all continues. As fossil fuels are continuously extracted and burned in vast numbers across the globe, high concentrations of greenhouse gases are released into our atmosphere, causing global warming; warming the atmosphere higher than average. This then begins to melt the large ice sheets known as glaciers. Glaciers are found in mountainous regions of every continent, except Australia. It is normal for glaciers to melt in warmer seasons, but they do so at a sustainable amount that mostly evaporates and becomes snow. However, due to our current higher than normal temperatures, glaciers are melting faster than they accumulate into snow. Thus, all this water finds its way to the sea, causing it to rise.
Other than glaciers, polar ice caps are also melting. In both the north and south poles, the melting land ice contribute to about a third of rising sea levels. Furthermore, the oceans are absorbing more than 90% of the atmosphere's heat as we continue to have record-breaking heat spells. When the temperature in water increases, it expands. So, not only are we receiving more water from glaciers melting, but it's also all expanding; rising the levels even faster.
different levels in different areas
Though the sea levels are rising, they are not doing so consistently throughout the Earth. This is based on several factors. Firstly, ironically, where glaciers and polar ice caps are melting, the sea level is at its lowest level. This is a phenomenon known as glacial isostatic adjustment that causes the water to rebound away from the source as the weight of it becomes lighter, which is mostly caused by varying deep depressions in the ocean floor, under the weight of the ice. So, in the warmer months, the water near the melting glaciers and ice caps are lowest, while elsewhere they are dramatically higher. Similarly, in cooler months, the water levels become more stable.
However, gravitational pull also affects where the water level is the highest. The Earth is not perfectly even everywhere, of course, and so neither is the gravitational pull. It differs in certain regions and depends on the rotation. But generally speaking, the heavier the gravitational pull, the deeper the water and vice versa. Finally, the water levels depend on the oceans' currents and where and to what coast they are moving the warmer water and glacial water toward. In other words, the water level could be extremely high in eastern Asia while it is slightly dropping along the western United States, and then be completely different six months later. Thus, the counting of sea levels rising is based on global averages.
the effects of vulnerability
What all this does, unfortunately, is allow the sea direct access to more vulnerable areas of coastal towns and cities during extreme storms that it did not have before. Because this was never an issue in the past, these developed areas are not prepared for the extremity of this impact. Also, keep in mind as global warming continues, we will be seeing more and more of these extreme storms, to boot. This becomes a major issue for infrastructure and with severe flooding, when we cannot adjust the current condition of entire cities for protection fast enough.
Some coastal cities that are more vulnerable to the sea levels rising than other due to gravity and currents, are doing as much as they can to combat the future of sea levels rising. Take Miami Beach, for example, spending $100 million on raising roads, installing pumps, and redirecting sewer connections. Considering that the current estimate of sea level rise will be 6 feet by 2100, and more than 49 feet by 2500 (again based on averages so much, much higher in certain areas at certain times of the year), I'd say Miami Beach is pretty smart.