FOCUS Sea Level Rise
Shored Up The accelerating creep of sea level rise.
NOAA
New U.S. regional sea level scenarios developed by NOAA and partners will help coastal communities plan for and adapt to risks from rising sea levels. This photo shows flooding in Norfolk, Va., on May 16, 2014.
By Bruce Buls, Editor-at-Large
T
ime was, SLR meant “single lens reflex,” at least to me and many others. That’s a type of camera with detachable lenses and a hinged mirror inside. Now, increasingly, it means “sea level rise.” It’s an acronym we may get used to because SLR (the wet kind) is upon us and will only rise as the planet continues to warm. Other acronyms to add to your vocabulary include EWL (extreme water level), HTF (high tide flooding) and MHHW (mean higher high water). For mariners, MLLW (mean lower low water) has long been the salient number to keep in mind as that represents the amount of water available to float your boat. Now, as sea levels rise, there’s more of that under your keel. At the same time, as MHHW goes up, so does shoreside flooding and ultimately inundation. When Hurricane Sandy hit New York and New Jersey in 2012, peak water levels measured by local tide
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gauges were between eight and nine feet above MHHW at the time. Tide gauges have been measuring the rise and fall of coastal tides for well over 100 years. There’s one in San Francisco Bay that dates back almost 150 years. Before digitization, tide gauges were large measuring sticks housed inside “tide houses” with pen-and-ink recorders. Now, acoustic sounding tubes and pressure sensors – or newer microwave radar water-level sensors – measure the tidal variations and transmit data directly to National Oceanic and Atmospheric Administration (NOAA) scientists. Satellite telemetry is also used to track water levels. MHHW is also the level used to visualize the reach of rising waters in NOAA’s Sea Level Rise Viewer, an online tool with maps of the entire U.S. coastline. With the viewer, users can see coastal areas’ current MHHW and then, using a slider, see the effects of rising sea levels in one-foot increments, up to 10'. It’s really quite dramatic, as you
move the slider higher, more area turns blue, meaning it’s inundated. It’s under water. The viewer isn’t predicting 10' of SLR specifically but shows it as a possibility and what it would mean. Ten feet, however, is within the higher range of projected SLR by 2150. The Sea Level Rise Viewer is a companion of the recently released 2022 Sea Level Rise Technical Report from NOAA. This report builds on a similar report from 2017, but with updated data, models and projections. One principal takeaway from the new report is a predicted sea level rise of about one foot between now and 2050. That’s about equal to the SLR of the previous 100 years, so the rate is accelerating. “Current and future emissions matter,” NOAA Administrator Rick Spinrad said during a video presentation that followed the report’s release, “but this will happen no matter what we do about emissions. If emissions continue at the current rate, it’s likely we see two feet of sea level rise by the end of the century, and that estimate is on the conservative side.”
BALLOONING SLR SLR is accelerating for three reasons: one, the oceans are expanding as they and the atmosphere are getting warmer; two, the oceans are filling up with more water from melting ice on land; and three, coastlines are generally sinking, a result of compaction and underground extractions of water and petroleum. (Except for Southeast Alaska, which is unique in that sea levels are dropping as the mountains are rising.) NOAA is the lead agency for this report — a multiagency and academic effort that included NASA, the Army Corps of Engineers, U.S. Geological Survey (USGS), Environmental Protection Agency (EPA), Federal Emergency Management Agency (FEMA), Department of Defense, and Florida International University and Rutgers University. These groups expect that the report and viewer will be used by coastal communities as they plan for these coming changes and develop mitigation strate-
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