FOR SOME IT WILL BE A MATTER O LUXURY, FOR OTHERS A MATTER OF FULFILLING THEIR DREAM OF LIVING ON THE WATER, BUT FOR ALL WILL BE A MATTER OF SURVIVING THE GLOBAL SEA LEVEL RISE.
The two major causes of global sea level rise are:
- 1. Thermal expansion caused by warming of the ocean (since water expands as it warms)
- 2. increased melting of land-based ice, such as glaciers and ice sheets.
- A. Globally, eight of the world's 10 largest cities are near a coast, according to the U.N. Atlas of the Oceans.
- B. The oceans are absorbing more than 90 percent of the increased atmospheric heat associated with emissions from human activity.
Lets start with the first cause: the warming of the oceans-Thermal expansion.
No mater what your believes about climate change are:
the facts and the raw reality is:
According to NOAA (National Oceanic and Atmospheric Administration)
I. IS SEA LEVEL RISING?
Yes, sea level is rising at an increasing rate
With continued ocean and atmospheric warming, sea levels will likely rise for many centuries at rates higher than that of the current century.
In the United States, almost 40 percent of the population lives in relatively highpopulation-density coastal areas, where sea level plays a role in flooding, shoreline erosion, and hazards from storms.
Globally, eight of the world's 10 largest cities are near a coast, according to the U.N. Atlas of the Oceans. Global sea level has been rising over the past century, and the rate has increased in recent decades. In 2014, global sea level was 2.6 inches above the 1993 average—the highest annual average in the satellite record (1993-present). Sea level continues to rise at a rate of about one-eighth of an inch per year.
Higher sea levels mean that deadly and destructive storm surges push farther inland than they once did, which also means more frequent nuisance flooding.
II. WHAT IS NUISANCE FLOODING?
High tide flooding, sometimes referred to as "nuisance" flooding, is:
- Flooding that leads to public inconveniences such as road closures, overwhelmed storm drains, compromised infrastructure and water quality.
- scientist say this type of flooding has increased 300 to 900 percent since 1960 and It is increasingly common as coastal sea levels rise more frequent within U.S. coastal communities than it was just 50 years ago.
- Several cities are experiencing it 10 to 20 additional days per year.
- Projections say the majority of coastal communities will experience 30 days of
tidal flooding annually by 2050.
III. WHICH IS THE COST OF SEVERE WEATHER CHANGE
a) SEA LEVELS ARE RISING AS SEAWATER WARMS AND EXPANDS
- Of the 203 weather disasters from 1980 to 2016, tropical cyclones have caused most damage: $560.1 billon total, with an average of $16 billon cost per event, and the highest number of deaths (3,210).
1. THERMAL EXPANSION
- First, although the oceans have an enormous heat storage capacity, if global atmospheric temperatures rise, the oceans will absorb heat and expand.
- A greater volume of ocean water due to thermal expansion will lead to a rise in sea level.
- The melting of floating ice will not affect sea level.
- Changes in sea level affect habitats and the flora and fauna they support.
- Changes in sea level impacts humans.
- As sea water heats up it becomes less dense and takes up more space, a process called thermal expansion. As the water takes up more space, sea levels rise. The study’s authors used seven years of temperature data from a set of buoys called Argo to calculate how much thermal expansion has contributed to sea level rise over that time.
- Thermal expansion will be responsible for between 70 and 75 per cent of sea level rise in the future.
- With continued ocean and atmospheric warming, sea levels will likely rise for many centuries at rates higher than that of the current century. In the United States, almost 40 percent of the population lives in relatively highpopulation-density coastal areas, where sea level plays a role in flooding, shoreline erosion, and hazards from storms.
- Globally, eight of the world's 10 largest cities are near a coast, according to the U.N. Atlas of the Oceans.
- Sea level rise at specific locations may be more or less than the global average due to local factors such as land subsidence from natural processes and withdrawal of groundwater and fossil fuels, changes in regional ocean currents, and whether the land is still rebounding from the compressive weight of Ice Age glaciers. In urban settings, rising seas threaten infrastructure necessary for local jobs and regional industries.
Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, landfills—virtually all human infrastructure—is at risk from sea level rise.
IV. WHAT'S THE DIFFERENCE BETWEEN GLOBAL AND LOCAL SEA LEVEL?
- Global sea level trends and relative sea level trends are different measurements. Just as the surface of the Earth is not flat, the surface of the ocean is also not flat—in other words, the sea surface is not changing at the same rate globally.
- Sea level rise at specific locations may be more or less than the global average due to many local factors: subsidence, upstream flood control, erosion, regional ocean currents, variations in land height, and whether the land is still rebounding from the compressive weight of Ice Age glaciers.
- Sea level is primarily measured using tide stations and satellite laser altimeters. Tide stations around the globe tell us what is happening at a local level—the height of the water as measured along the coast relative to a specific point on land. Satellite measurements provide us with the average height of the entire ocean.
- Taken together, these tools tell us how our ocean sea levels are changing
2. Melting of land-based ice
Let’s first see what’s the difference between land base ice and sea base ice:
a. Land ice and sea ice
comprise the majority of the polar regions on Earth.
The most basic difference is that sea ice forms from salty ocean water, whereas land ice (ice sheets and glaciers) form from fresh water or snow. Land ice can be labelled as ice sheets whereas sea ice can be labelled as ice shelves. They vary greatly in quantity due to seasonal changes in temperature. An increase in global temperature caused by anthropogenic warming influences the quantity of polar ice.
(a) sea ice
Sea ice forms in the winter months and melts in the summer
months, however in certain regions it remains year round. Roughly 15% of the world's oceans are covered by sea ice during a portion of the year.
Sea ice is white which means it has a highly reflective surface,
thus it has a high albedo. Roughly 80% of the sunlight that hits the ice reflects into space. As the sea ice melts in the summer, and instead of reflecting, the ocean absorbs 90% of the sunlight.
This absorption heats up the ocean causing further more melting
of ice. This is an example of a positive climate feedback, which is part of why climate change effects are hard to predict.
Both types of ice range over vast areas of the polar regions.
Global sea ice on average covers nearly 25 million km2, the same size as the North American continent.
b. Land ice.
Which can become sea ice when chunks of ice that break off and fall into the ocean (and become icebergs).
vs sea ice Lake ice is also considered land ice.
Frigid, low density fresh water stays at the surface of a lake or river, forming a layer of ice on the surface. Land ice differs from sea ice in the way that it is formed. Fresh water becomes less dense as it approaches the freezing point. In contrast, sea ice forms quite slowly, compared to freshwater ice, because the saline water tends to sinks away from the cold surface before it cools enough to solidify. Ice sheets and glaciers cover approximately 15 million km2, roughly equivalent to 10% of the Earth's land surface area. While still large, land ice only covers two thirds as much surface area as sea ice covers.
Consequences of Melting
As ice melts and becomes water, the volume of water gets
displaced relative to the volume of water it would contribute as
melting occurs. Thus, when sea ice, there is no change in sea
This is due to Archimedes' principle which states that if a body is immersed in a fluid, that body is lifted up by a buoyant forces equal to the weight of the fluid that is displaced.
With land ice, the ice wasn't displacing any water. When the land ice melts, additional water is added into the ocean, causing the sea level to rise.
The intensity of sea level rise depends on the quantity of melt
For example, if the entire West Antarctic ice sheet melted, the sea level would increase by 5 meters.
To put that into perspective:
- a 1-meter level sea rise would displace 100 million people who live along coastal lines.
- Ice shelves act as a reinforcement, preventing glacial ice from reaching the ocean. Once the barrier is gone, glacial ice melt entering the ocean would increase the sea level.
- Greenland and Antarctica combined, contain about 75% of the world's
fresh water, which is enough to raise sea level by over 75 meters, if all
the ice were restored to the oceans.
- There are more consequences than just sea level rise to due land and sea ice melting. Differences in salinity and temperature impact global ocean circulation. These variations in ocean temperature and salinity can disrupt and threaten marine species that are dependent on the ocean due to the ocean being delicate to change. Fresh water is less dense than salt water and warm water is less dense than cold water; these differences cause circulation in the ocean which is referred to as thermohaline circulation.
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