Tag Archives: sea level rise

Map of sea level predictions can assist waterfront owners

A sophisticated analysis of sea-level rise in Puget Sound and along the Washington Coast offers shoreline residents and land-use planners a new map-based tool to assess potential flood hazards for the coming years.

Click on map to access online interactive map
Map: Washington Coastal Hazards Resilience Network

Sea-level rise depends on two factors: how fast the oceans rise and the rate of vertical land shifts. Uplift, such as what occurs along the Washington Coast, slows the rate of sea-level rise relative to waterfront property. Subsidence, which occurs in Central Puget Sound, results in elevated tides sooner than in stable or uplifting areas. One map on this page shows the measured uplift and subsidence and another shows the uncertainty in that measurement.

Ian Miller, a coastal hazards specialist at Washington Sea Grant, has worked on studies that describe sea-level rise in Island County and on the Olympic Peninsula. The new report, titled “Projected Sea Level Rise for Washington State” (PDF 10.4 mb) goes well beyond what he and his colleagues have done before. It takes a more detailed look at where the land is uplifting and subsiding, according to Miller, the lead author on the new report that involves work by scientists at Sea Grant and the University of Washington’s Climate Impacts Group.

The result is a prediction of sea-level rise at 171 locations, covering every shoreline in Washington state — as opposed to more general predictions made in previous studies, including regional and national studies by others.

The goal this time, Ian told me, was to develop an analysis that could be used for predicting future high tides at any shoreline segment in the state. Actual sea-level rise will depend on how much humans can reduce greenhouse gases in the coming years and other factors. Results in the report are given for both high and low scenarios based on climate models, and the findings are presented as probabilities of occurrence.

In Bremerton, for example, the analysis predicts that there is a 90 percent chance that the sea level will rise by 6 inches or more by 2070. At the same time, the probability is 50 percent that the rise will be at least 1 foot by 2070 and 10 percent that it will reach 1.7 feet by that year. That’s under the low greenhouse gas scenario.

Under the high scenario, there is a 90 percent chance that the sea level in Bremerton will reach 7 inches by 2070, a 50 percent chance that it will reach 1.2 feet and a 10 percent change that it will reach 1.9 feet.

In some cases, a rise in the high tide level by just 6 inches can result in serious property damage, especially if winds and waves increase as a result of more intense storms. For Bremerton, there is a 16 percent chance that this level will be reached by 2030, a 50 percent chance it will be reached by 2040 and a 75 percent chance it will be reached by 2050, according to the report.

The new report can help landowners think more clearly when deciding where to locate new buildings on their property, whether to move existing buildings and what to do about failing bulkheads. I covered the issue of planning for sea-level rise for the Encyclopedia of Puget Sound. Check out:

And in Watching Our Water Ways:

Clicking on the map at the top of this page will take you to the online interactive map. Looking at the online map, click on any shoreline location to download the data tables, which may look a little intimidating at first. But don’t worry. Just use the tabs at the bottom to pick a high (RCP 8.5) or low (RCP 4.5) greenhouse gas scenario. You will see two tables for each scenario. In the top table, pick a year (vertical list) and a probability (horizontal list) to get the projected sea level rise (in feet). In the bottom table, pick a year along with sea level rise to get the probability of that level being reached.

Sea-level rise is accelerating as time goes on, as predicted by climate models and supported by recent studies. (See the report on satellite readings in the Proceedings of the National Academy of Sciences.) One hundred years from now, there is a 90 percent chance that sea level will be at least one foot higher in Central Puget Sound and a 50 percent chance that it will be at least two feet higher.

Unlike any previous report in Washington, predictions for changes in vertical land movement in the new report are based on three different sources of information: variations in tide gauges, “leveling surveys” used by highway engineers and data from continuous global positioning satellites. For the satellite data, the analysis of sea-level rise took into account separate assessments of land movement calculated by five different organizations.

By analyzing the sources of data for vertical changes across the landscape, the researchers were able to provide a range of uncertainty for each of their 171 shoreline locations. Knowing the level of confidence for water reaching a given level in a specified amount of time can help people decide whether they are willing to accept the risk or begin planning for the future.

I’ve gone through the map, looking at a variety of waterfront locations in Washington state. In the lists below, I’ve grouped the cities to show how much the sea level is expected to rise by 2050, using a 50 percent probability and a high greenhouse gas scenario.

0.1 foot
Neah Bay

0.3 foot
Sekiu

0.4 foot
Ocean Shores, Ozette

0.5 foot
Aberdeen, Point Roberts, Port Angeles

0.6 foot
Bellingham, La Push, Queets, San Juan Island

0.7 foot
Anacortes, Hoodsport, La Conner, Sequim

0.8 foot
Bremerton-Port Orchard-Silverdale, Everett, Gig Harbor, Hansville, Port Townsend, Poulsbo-Suquamish-Bainbridge, Seattle, Shelton, Tacoma, Vashon Island (most), Whidbey Island

0.9 foot
Ballard, Edmonds, East Vashon-Des Moines, Federal Way, Port Ludlow, Shelton

1.0 foot
Kingston, Olympia

Additional information on this project:

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Waterfront property owners face options in response to sea-level rise

Rising sea levels and isolated floods will be an increasing challenge for waterfront property owners, according to experts I interviewed for a story published this week in the Encyclopedia of Puget Sound.

The Vechey home and bulkhead before the big move. // Photo: John Vechey

Changing conditions call for property owners to consider their options with regard to their shoreline — not just for today but for the long run. What I learned while researching this story is that every waterfront site will respond differently as the highest tides go higher and higher.

Before I started my inquiry, I thought the obvious answer would be for people to build taller and stronger bulkheads — despite well-known environmental damage. And that may be the only answer for some. But for others, that approach could be a waste of money, as bigger walls degrade the owners’ enjoyment of the beach as well disrupting natural systems. Alternatives include moving or raising a house or even replacing a bulkhead with “soft shore” protections.

After the home was moved back from shore and the bulkhead removed. // Photo: John Vechey

Sea levels in Puget Sound are rising slowly at this time, with the actual rate dependent on location. We live in a tectonically active area, with major movements along continental plates. As a result, the ground is sinking in most areas around Puget Sound, adding to the relative rise in sea level.

In Seattle, the sea level has risen about 9 inches since 1900 and is expected to rise an additional 4 to 56 inches (4.75 feet) by 2100. The uncertainty reflected in that range relates to whether greenhouse gases continue to increase, thus accelerating the rate of melting of land-based ice in the polar regions.

Some changes can be expected regardless of the human response over the next 80 years. For example, one analysis looking at Whidbey Island suggests that there is a 99 percent chance that by 2040 — just 13 23 years from now — sea level will be at least 2.4 inches higher than today with a 50 percent chance that it will be 7.2 inches higher. After 2040, the tides will keep rising even faster. Take a look at the related story “Average high tides are creeping higher in Puget Sound.”

John Vechey of Orcas Island, who I featured in my story, took sea level into account when deciding whether to remove his bulkhead while seeking to improve the beach for family activities and for the environment. His solution was to move his house and give the beach more room to function naturally.

Moving a house will not be the answer for everyone, but I can safely say that everyone should consider their long-term picture before making any investments that will last a lifetime — and that includes changes to the shoreline.

I believe it is generally possible, certainly with professional help, to calculate elevations for the house and any low spots on the property, add one to four feet above the current high-tide mark, and then consider tidal surge, which is the wave height caused by weather conditions. In some counties, professional help is available if you are considering whether to remove a bulkhead. Check out the “Shore Friendly” website and “Resources in Your Area.”

At this time, future sea levels do not enter into regulatory considerations about where a person can build a house. One problem is the uncertainty surrounding the amount that sea levels will actually rise. But some environmental advocates say it is time to require additional setbacks, not only to protect the environment as tides push back the natural beach but also to protect homeowners from future losses.

For some people, sea-level rise is a distant worry, but for others the threat is just around the corner. I was reading this morning about how high tides are already affecting Naval Station Norfolk. Check out “Rising Seas Are Flooding Virginia’s Naval Base, and There’s No Plan to Fix It” by Nicholas Kusnetz of Inside Climate News.

A new Government Accountability Office report, released yesterday, cites estimates of future property damage totaling between $4 billion and $6 billion per year in the U.S. as a result of sea-level rise and more frequent and intense storms. The report outlines the need for a coordinated federal response.

Sen. Maria Cantwell discusses the new GAO report and calls for better planning in the video below.

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Shoreline bulkheads impose changes on
the natural ecosystem

It goes without saying that wood, rock or concrete bulkheads built along the shoreline are not natural. They certainly don’t look like any structure formed by nature. And when the water is pushing up against them, waves bounce around and splash back instead of rolling up on shore.

Bulkhead

I have never had any trouble understanding some of the problems caused by bulkheads. I imagine little juvenile salmon swimming along the shoreline, working their way toward the ocean. In shallow water, these little fish can stay away from the bigger fish that want to eat them. But bulkheads create a stretch of deeper water, where predatory fish can swim in close and devour the little ones.

I’ve been told that bulkheads cause other problems as well, such as blocking shoreline erosion. But isn’t that what they are designed to do? What’s the problem? As I’ve learned — especially over the past few months — natural erosion provides the sands and gravels needed for healthy beaches. Natural beaches also collect driftwood, which provides additional habitat for a variety of creatures.

As many readers know, I now work half-time for the Puget Sound Institute, a University of Washington affiliate that publishes the Encyclopedia of Puget Sound. We’ve been working on a series of articles about bulkheads — formally known as shoreline armoring — and I’m more convinced than ever that bulkheads really do cause problems.

Surf smelt Photo: Wikimedia commons
Surf smelt // Photo: Wikimedia commons

The first story in the series, released this week, describes the effects of bulkheads on spawning habitat for surf smelt and sand lance, two kinds of small fish that are an important food source for salmon, birds and marine mammals. Check out my story, “Spawning habitat for forage fish being lost to rising tides.”

As sea levels continue to rise, the high-tide and low-tide lines move to higher elevations on the beach — until the high-tide line reaches the bulkhead. For many bulkheads, the high-tide line is already there. At that point, the rising sea level continues to push the low-tide line to higher and higher elevations, reducing the spawning habitat for fish that lay their eggs in the intertidal area.

This shrinking habitat is known as “coastal squeeze” or “beach squeeze.” Recent studies suggest that where bulkheads are located, Puget Sound could lose 80 percent of this spawning habitat by the turn of the century, based on average predictions of sea-level rise.

On beaches without bulkheads, the high-tide line would move steadily inland, helping to maintain the critical habitat for forage fish, according to Timothy Quinn, chief scientist for the Washington Department of Fish and Wildlife.

“Everywhere in Puget Sound, there will be beach squeeze when you don’t allow things to equilibrate on the land side,” he told me. “What used to be exposed beach (during the tidal cycle) will no longer be exposed.”

It turns out that many bulkheads constructed through the years were never needed to prevent erosion, because they were built to protect homes in areas where erosion is minimal. Future stories in our series will cover this issue, including the prospect of removing existing bulkheads to improve shoreline habitats. Unfortunately, sea level rise adds a new twist to the discussion. Still, the best advice when building a new house is to keep the structure back from the water’s edge.

In addition to the general story about beach squeeze, I wrote a sidebar about a study that looked at the effects of this phenomenon on 15 different beaches in the San Juan Islands. See “Forage fish are losing places to lay their eggs.”

Meanwhile, this initial installment of the Shoreline Armoring Series includes a nice piece by science writer Eric Scigliano called “Shoreline armoring’s effect on the food web.” In this story, Eric looks at a broad spectrum of effects caused by bulkheads. He reports on an involved study that focused on a series of paired beaches — one with a bulkhead and one without — located in various parts of Puget Sound.

Most of the studies that we will report on during this series were funded by the Environmental Protection Agency through grants coordinated by the Washington Department of Fish and Wildlife. The plan is to release about two additional stories each week over the next two weeks.

Surf smelt spawning zone below low tide mark Illustration: Washington Department of Fish and Wildlife
Surf smelt spawning zone below high tide mark
Illustration: Dan Penttila, Washington Department of Fish and Wildlife

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NASA researchers measure sea levels, predict faster rise

A new worldwide map of sea level rise, plotted with precision satellite instruments, shows that the Earth’s oceans are rising faster with no end in sight.

Sea levels have gone up an average of 3 inches since 1992, with some locations rising as much as 9 inches. Meanwhile, some limited areas — including the West Coast — have experienced declining sea levels for various reasons.

Sea level change over 22 years. Map: NASA
Sea level change over 22 years. (Click to enlarge) // Map: NASA

Two years ago, climatologists released an international consensus, which predicted a sea-level rise of between 1 and 3 feet by the end of this century. It was a conservative estimate, and new evidence suggests that ocean waters are likely to meet or exceed the top of that range, possibly going much higher, according to four leading researchers speaking at a news conference yesterday.

The implications are huge and growing more important all the time. At a minimum, waterfront property owners and shoreline planners need to begin taking this into consideration. It doesn’t make sense to build close to the shoreline if extreme high tides will bring seawater to one’s doorstep.

If we hope to avoid local extinctions of key intertidal species, we must start thinking about how high the waters will be in 50 to 100 years.

For clues to the future, we can watch Florida, where vast areas stand at low elevations. Even now, during high tides, Miami is beginning to see regular flooding in areas that never got wet before. This is the future of low-lying areas in Puget Sound, such as estuaries. In the Pacific ocean, the threat of inundating complete islands is becoming very real.

Along the West Coast, sea levels have actually declined over the past 20 years, largely because of the cooling effect of the Pacific Decadal Oscillation, a warming/cooling cycle that can remain in one phase for decades. The cycle appears to be shifting, with the likely effect that sea levels on the West Coast will soon rise as fast or faster than the worldwide average, according to Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

Global sea level has been measured accurately and continuously by satellites since 1993. Graphic: Steve Nerem, University of Colorado
Global sea level has been measured accurately and continuously by satellites since 1993.
Graphic: Steve Nerem, University of Colorado

The cause of sea level rise is attributed to three factors. Scientists estimate that roughly one-third of the rise is caused by thermal expansion of ocean waters, which absorb much of the energy from global warming. Another third comes from the melting of the massive Greenland and Antarctic ice sheets. The remaining third comes from the melting of mountain glaciers throughout the world. Researchers at yesterday’s news conference said they expect the melting to accelerate.

Measuring the change in sea-level rise has become possible thanks to advanced technology built into altimeters carried aboard satellites. The instruments can distinguish changes in elevation as small as one part in 100 million.

“The instruments are so sensitive that if they were mounted on a commercial jetliner flying at 40,000 feet, they could detect the bump caused by a dime lying flat on the ground,” said Michael Freilich, director of NASA’s Earth Science Division.

While sea level rise can now be measured, predicting the rate of future rise is difficult, because much of the melting by ice sheets occurs out of sight under the water.

The Greenland ice sheet covers 660,000 miles — nearly the size of Alaska. Satellite measurements have shown that an average of 303 gigatons of ice have melted each year over the past decade. The Antarctic ice sheet has lost an average of 118 gigatons per year, but some new studies suggest it could begin to melt much faster.

In Greenland, researchers are reporting that one of the largest chunks of ice ever to break away from land cleaved from the Jakobshavn glacier in a “calving” event that left researchers awestruck. More than 4 cubic miles of ice was loosed quickly into the sea. Check out the news release by the European Space Agency.

“This is a continuing and evolving story,” glaciologist Eric Rignot said during yesterday’s news conference. “We are moving into a set of processes where we have very tall calving cliffs that are unstable and start fracturing and break up into icebergs …

“We have never seen something like this on that scale before,” said Rignot, associated with JPL and the University of California at Irvine. “Personally, I am in awe at seeing how fast the icefall, the calving part of the glacier, is retreating inland year by year.”

Other new information from NASA, including lots of graphics:

The following video tells the basic story about sea level rise.

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Seafood supplies may be disrupted by global warming

The world’s fish populations are already being affected by global warming, and the human population faces long-term consequences with respect to seafood supplies and local economies that depend on them, according to a statement from the United Nations Food and Agriculture Organization.

These conclusions are coming out of a four-day conference of 200 experts and policymakers focused on the marine fisheries issue. The conference, in Rome, Italy, comes to a close today.

Changes already being seen, as reported in a technical summary (PDF 160 kb) written prior to the conference:

  • Oceans are warming, while currents, such as those affected by El Nino, seem to be changing. This could have implications for the West Coast.
  • Salinity is changing in surface waters, with warming areas of Earth growing more salty from evaporation, while more northern and southern areas grow less salty from increased rain along with ice and snow melt.
  • Global sea level has been rising since 1961 with an accelerated rate since 1993.
  • Fish distribution has been changing, generally with both warm- and cold-water species moving closer to the poles.

Predictions for the future:

  • Changes in fish availability will change at the local and regional levels.
  • Markets for various seafoods could grow unstable, as distribution systems try to respond to shifts in supply at various locations.
  • Prices for various seafoods could fluctuate with uncertain supplies, and those in the industry could see their jobs disrupted.
  • Countries where people eat a lot of seafood may face changes in nutrition with related health implications.

The technical summary also includes this statement:

At both the local and global levels, fisheries and aquaculture play important roles in providing food and generating income. Some 42 million people work directly in the sector, the great majority in developing countries. Adding those who work in associated processing, marketing, distribution and supply industries, the sector supports several hundred million livelihoods.

Aquatic foods have high nutritional quality, contributing 20 percent or more of average per capita animal protein intake for more than 2.8 billion people, again mostly in developing countries.

Fish is also the world’s most widely traded foodstuff and a key source of export earnings for many poorer countries. The sector has particular significance for small island states.

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