Sea Level Rise

Climate explained: why coastal floods are becoming more frequent as seas rise

The Conversation 11/19/19

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

UCAR 2019

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

AAAS 7/24 2019

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

DailyKos Greenland Melting 5/06/2019

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.”