Sea level is rising more rapidly in the Humboldt Bay region than in any other place on the US West Coast. Cal Poly Humboldt’s Center for Sea Level Rise has been looking at the implications and last Monday, the San Francisco Chronicle gave us feature treatment.Sea level is rising more rapidly in the Humboldt Bay region than in any other place on the US West Coast. Cal Poly Humboldt’s Center for Sea Level Rise has been looking at the implications and last Monday, the San Francisco Chronicle gave us feature treatment.Sea level rise became news in the 1970s. Studies were published and in 1988 the UN formed the Intergovernmental Panel on Climate Change was formed. Since 1993, satellite altimetry has provided a global picture of the rising oceans. The current estimate of average sea level rise is 3.4 millimeters (.13 inches) per year. There is no gray area here, it is a measured fact.But the ocean isn’t a bathtub, and the rise is not uniform, rising more rapidly in some areas and dropping in others. How water level changes locally is a function of many variables. The three most important are thermal expansion, the supply of water, and deformation of the sea floor.Water expands as it warms. A warmer ocean raises sea level with no additional water. Expansion rates are complex and depend on salinity, temperature, and pressure. There are seasonal changes and longer ones. Thermal expansion in strong El Niño years can raise the background tide levels by nearly a foot. Added water comes from three main sources: valley glaciers, the Greenland ice sheet, and the Antarctic ice sheet. I called them the three dominos when I taught about sea level rise. Alas, the valley glaciers are nearly gone and much of their contribution is already in the ocean. Melting of the Greenland ice sheet is well underway and all eyes are now on Antarctica. It will be the primary driver of sea level rise over the next century.Read More
