Sea Level Rise
Abrupt Sea Level Rise Looms As Increasingly Realistic Threat
BY NICOLA JONES • MAY 5, 2016 Yale Environment 360
Ninety-nine percent of the planet’s freshwater ice is locked up in the Antarctic and Greenland ice caps. Now, a growing number of studies are raising the possibility that as those ice sheets melt, sea levels could rise by six feet this century, and far higher in the next, flooding many of the world’s populated coastal areas.
The Earth has seen sudden climate change and rapid sea level rise before. At the end of the planet’s last glaciation, starting about 14,000 years ago, sea levels rose by more than 13 feet a century as the huge North American ice sheet melted. But researchers are hesitant about predicting similarly rapid climate shifts in our future given the huge stakes involved: The rapid collapse of today’s polar ice sheets would erase densely populated parts of our coastlines.
“Today, we’re struggling with 3 millimeters [0.1 inch] per year [of sea level rise],” says Robert DeConto at the University of Massachusetts-Amherst, co-author of one of the more sobering new studies. “We’re talking about centimeters per year. That’s really tough. At that point your engineering can’t keep up; you’re down to demolition and rebuilding.”
New Data Shows an ‘Extraordinary’ Rise in U.S. Coastal Flooding
<embed> https://www.nytimes.com/2020/07/14/climate/coastal-flooding-noaa.html?fbclid=IwAR2yvXDbrCX14LqlNi129dsB4pTfzwKr_KC-4okBUgw8fset1nJw_jVrlmk </embed> NY Times 7/14/2020
Rising seas are bringing water into communities at record rates, the National Oceanic and Atmospheric Administration said Tuesday. The increase in high-tide flooding along the Atlantic and Gulf Coasts since 2000 has been “extraordinary,” the National Oceanic and Atmospheric Administration reported, with the frequency of flooding in some cities growing fivefold during that time. That shift is damaging homes, imperiling the safety of drinking water, inundating roads and otherwise hurting coastal communities, the agency said. NOAA defines high-tide flooding, also called sunny-day or nuisance flooding, as water rising more than half a meter, or about 20 inches, above the normal daily high-tide mark. The frequency of that flooding has increased because of rising sea levels, which were roughly 13 inches higher nationally last year than in 1920, the agency reported.
Island 'drowning' is not inevitable as sea levels rise
<embed>https://phys.org/news/2020-06-island-inevitable-sea.html</embed>
The results show that islands composed of gravel material can evolve in the face of overtopping waves, with sediment from the beach face being transferred to the island's surface. This means the island's crest is being raised as sea level rises, with scientists saying such natural adaptation may provide an alternative future that can potentially support near-term habitability, albeit with additional management challenges, possibly involving sediment nourishment, mobile infrastructure and flood-proof housing.
Climate explained: why coastal floods are becoming more frequent as seas rise
<embed>https://theconversation.com/climate-explained-why-coastal-floods-are-becoming-more-frequent-as-seas-rise-127202</embed>
The background sea level rise has been only 20cm around New Zealand’s coasts so far, but even that makes a noticeable difference. An apparently small rise in overall sea level allows waves generated by a storm to come on shore much more easily. Coastal engineers use the rule of thumb that every 10cm of sea level rise increases the frequency of a given coastal flood by a factor of three.
The occurrence rates change so quickly because in most places, beaches are fairly flat. A 10cm rise in sea levels might translate to 30 or 40 metres of inland movement of the high tide line, depending on the slope of the beach. So when the tide is high and the waves are rolling in, the sea can come inland tens of metres further than it used to, unless something like a coastal cliff or a sea wall blocks its way.
Rising Sea Level
<embed>https://scied.ucar.edu/longcontent/rising-sea-level</embed>
Change in global sea level in the future is predicted to occur at a faster rate. The amount of sea level rise depends in large part on the amount of warming. According to the IPCC Forth Assessment Report (2007) by the mid-2090s global sea level may be 22 to 44 centimeters above its 1990 level and rising at about 4 mm per year.
Greenland Ice Sheet Melt from European Heat Wave
Twitter Xavier Fettweis 7/29/2019
A heat wave is starting tomorrow over Greenland with Tmax reaching 25°C in tundra. The integrated anomaly of melt over the next 5 days (resp. over Summer 2019) will be 40Gt ~0.11mm (resp. ~0.65mm) sea level equivalent. Summer 2019 = what the models project for 2050 using RCP85.
Tidewater Glaciers Melting Faster Than Expected
<embed>https://www.aaas.org/news/tidewater-glaciers-melting-faster-expected</embed>
Alaska's LeConte Glacier is melting underwater at rates nearly a hundred times greater than what is currently estimated, according to a detailed sonar survey of the glacier's submerged surfaces.
The newly observed melt rates are up to two orders of magnitude greater than those calculated by some current predictive models. The findings, published in the July 26 issue of Science, are the first based on direct subsurface measurements of a tidewater glacier and suggest that similar glaciers worldwide may be in far "hotter water" than previously known. "Beyond proving that [the method] is doable, we found that melt rates over most of the glacier were extremely high compared to those predicted by theory," said Sutherland, and that they changed seasonally, increasing from spring to summer. For example, melt rates based on these direct observations suggest melt rates of more than eight meters per day in August, whereas theoretical models predict a single meter of daily change.
Based on the physics of ice melt along the ice-ocean interface, Sutherland is confident that similar submarine melt is occurring elsewhere, particularly at the far larger tidewater glaciers in Greenland or west Antarctic Peninsula.
Greenland unraveling rapidly as feedback loops bring the ice sheet closer to the tipping point
Feedback loops make the problem of a warming Arctic that much worse and according to Thomas Growther, a professor at the Department of Environmental Systems Science of ETH Zurich, “It’s already begun, the feedback is in process”. Yahoo news, reports that “carbon dioxide and methane emissions from thawing soils are “accelerating climate change about 12 to 15 percent at the moment,” and said past IPCC reports that left out the feedback “were way more optimistic than they should have been.”
