by Lizzie Yarina, Masters of Architecture/Masters of City Planning at MIT
Mean sea level is a gauge of where and how people live. Variations in sea level instigate various forms and flows of occupation as humans adapt to the ocean’s various topographies. Historically, migration patterns associated with climactic changes were unbounded (or at least less bounded) by hard geopolitical lines. When one atoll in the South Pacific suffered a storm surge or lost its fresh water source, islanders would easily mobilize to another . Increasingly rapid changes in mean sea level, and associated effects on global water cycles, require new means of migration across predefined borders. Flows of population away from climactic risks and towards areas of safety or ice-melt related opportunity establish new poles of migration, defining new territories and questioning existing ones.
Mean sea level is studied and established from orbital space. Satellites provide a huge repository of data about the earth, and most global-scale oceanic properties are measured from the outer atmosphere. At this time, that includes surface temperature (SST), topography, salinity (SSS), the height and spectra of waves, surface wind speed and direction, ocean color, continental and sea ice extent, ocean mass, and surface currents . Beginning with Seasat in 1977, satellites have been creating a body of data surrounding the surface conditions of the ocean. While it is difficult for satellites to penetrate the often murky depths of the ocean, these surficial conditions can provide information about what is happening below. For example, satellite photographs of ocean color can provide information on algae blooms, and sea level data can be used in the analysis of ocean floor topography.
Sea level, and its variation from Mean Sea Level (MSL) (a global average) is measured through satellite altimetry. The first satellite altimeter was Topex/Poseidon, a joint collaboration between CNES (Centre National d’Etudes Spatiales) and NASA. The data collected in their first cycle in 1992 corresponded with prior data collected at the ocean surface level, with an extreme increase in speed and accuracy. Although Topex/Poseidon was decommissioned in 2005, a series of other satellites, beginning with Jason-1 in 2001, have served to both supplement and replace retired iterations. Topex/Poseidon’s circulation about the earth tracked from 66 degrees north to 66 degrees south, thus covering all but 10% of the ocean’s area. Cycles repeated every 10 days. Jason-1 was introduced midway between Topex/Poseidon’s tracks, such that the resolution of data collection was doubled. There are currently four satellite altimeters in orbit, operated by more than as many national sea and space agencies (including CNES, NASA, and NOAA). Seven new satellite altimetry deployments are planned for the next decade, which will include technology improving the speed and resolution of data collection.
AVISO, the representation and data arm of CNES, the French space agency, annually outputs maps showing current sea level and ongoing trends . These maps clearly show that sea level is not, in fact, level. Levels at any given moment, and rates of change over time, vary according to regional and global processes including currents, ice melt, and the gravitational force of the earth and moon. These maps contributes to knowledge on the interconnectedness of long term climactic patterns, global tides, and perhaps most importantly, global sea level rise. Comparison of the 2012 map to prior iterations demonstrates a 2” increase in MSL since 1993. This is due to factors including glacial melt and the thermal expansion of water with rising temperatures . The 2012 map shows the effect of La Nina in the Pacific, raising sea level its western tropics, as well as effects of the Decadal Pacific Oscillation on its opposite edge. This map also shows the highest MSL to date.
MSL is an index of a changing climate, but also of patterns of habitation and movement. This redistribution of global waters has specific impacts on local geographies and livelihoods, ultimately resulting in the redistribution of human populations. [...]
"Means + Migrations" research booklet: issuu.com/oceanicturn/docs/means_and_migrations_inside_pages
This research video was created as part of The Oceanic Turn Advanced Seminar, Harvard Graduate School of Design, Spring 2014: gsd.harvard.edu/#/academics/courses/adv-09132-spring-2014.html