Week 10: Sea Level Rise

The Rise and Fall of Atmospheric CO2, Global Average Temp. and Sea Level

Atmospheric CO2 varied between 180 ppm and 280 ppm (now at 400 ppm) Global average temperature varied by about 5°C Global sea level varied by about 100 m

Variations of Sea Level Rise due to land/water interface

Depending on the rates of vertical land motion relative to changes in sea level, observed local sea level trends may differ greatly from the average rate of global sea level rise, and vary widely from one location to the next. For instance, in areas of the northern Gulf of Mexico where significant subsidence is occurring, relative sea level trends reflect an increase of greater than 10 mm/yr in some locations, while areas of southeastern Alaska reflect a decrease in relative sea level because the region is dominated by isostatic rebound, or regional uplift of the land caused by the retreat of the glaciers.

Why is San Francisco Bay area infrastructure is especially vulnerable to sea level rise?

Large portions of San Francisco, including the entire financial sector, were built on reclaimed land. This was possible because the bay is very shallow (only 12 feet deep). Since engineers worked to build up previously underwater land to expand the city, these portions of the city were only built up to just above sea level to save resources.

Global temperature since the industrial era

.85 deegree celsius in global average temperature most of the heat is being taken up by the ocean

Average historical sea level trend in North America

0-33 mm per year

Sea Level Rise Rates in the past century

1.7-1.8 mm

How will impending sea level rise affect California's limited freshwater supply? What solution has been proposed?

26 million people, 2/3 of the population of California, get water from the Sacramento-San Joaquin estuary, which sits below sea level. Even 1 foot of sea level rise will contaminate this river delta with salt. One solution for this problem is to use sand harvested from nearby sea beds to build a huge dam under the golden gate bridge blocking the San Francisco bay from the ocean entirely and turning the bay into a freshwater lagoon.

In the documentary, we learned that half of the rice growing lands in Bangladesh would be flooded under a modest 3 ft sea level rise. What kind of engineering solutions could be designed to save this cropland? Who do you think should pay for it?

Potential engineering solutions to save low-lying areas from sea level rise: levies, dams, sea walls, seawater pumps. These solutions are costly, and in some of the areas most vulnerable to rising seas (especially Asia), the people will not be able to afford this infrastructure. Maybe a Carbon tax could be imposed to help fund these engineering solutions

Consequences if New Orleans and Miami are abandoned due to sea level rise

An entire city worth of marine debris will likely create huge problems with the ecosystem, accumulation of trash in the ocean, and even human safety issues for swimmers and boats. Also, these large areas of coastline would be rendered unusable.

Storm Surges

Storms can have a big impact on local water levels in coastal areas. A storm surge happens when water is pushed toward the shore by high powered winds from a storm such as a hurricane. The storm interacts with the normal tide to create a storm tide that can increase the normal water height by 4 to 5 meters (15 feet) or more. These events can cause extreme flooding in coastal areas. Most coastlines in the United States are only 3 meters (10 feet) or less above mean sea level, which means that storms can be very dangerous for people who live near the coast.

Sea Level Rise since the industrial era

There has already been a 20cm (about 8 inches) rise above pre-industrial era levels IPCC* 4 Report that came out about 5 years ago predicted about 40 cm above pre-industrial era levels by the end of century IPCC* 5 report that came out about a year ago has placed the expected rise to 1 meter above pre-industrial level by the end of this century

Contributions to Sea Level Rise

Thermal expansion is the greatest contributor to the current sea-level increase, followed by melting land ice. -Melting of glaciers and continental ice masses, such as the Greenland ice sheet, which are linked to changes in atmospheric temperature, can contribute significant amounts of freshwater input to the Earth's oceans. Additionally, a steady increase in global atmospheric temperature creates an expansion of saline sea water (i.e., salt water) molecules (called thermal expansion), thereby increasing ocean volume.

where on land did paleontologist and astrobiologist Peter Ward find evidence of coral life? Why did he find it there, and what does that mean?

Ward found paleontological evidence of coral in an abandoned stone quarry in Florida. Since Florida hasn't experienced any volcanism or mountain range building that would cause these stones to rise up, this is evidence that this part of Florida used to be covered by at least 10 feet of water. This indicates that in the past, sea levels were much higher, so it is possible they could rise that high again in the future.

Same situation in Antartica

Warming coastal currents move the grounding line back and cause the floating ice sheets to thin and break up and allow ice behind to flow forward into the sea. Note: Antarctica contains enough ice to raise global sea level by 60 m (200 ft)

Surface Melt Moulin in Greenland

a vertical shaft carrying water to ice sheet base. This lubricates the ice sheet and allows increased flow over the landmass. Note: Greenland contains enough water to raise sea level by 5 meters.

Subsidence

or the sinking of land. Scientists believe this is occurring because the rapid accumulation of sediments carried to and deposited on the Mississippi delta weighs down the Earth's crust in that area.