From Samish Island to the Skagit River delta, marine shorelines in Skagit County will likely see about 2 feet of sea level rise by 2100, according to a study released Monday.
The study, “Projected Sea Level Rise for Washington state,” uses the latest sea level rise science and takes into account land movement. It highlights the most likely scenario for 171 sites.
The study provides the most accurate and most user-friendly data on sea level rise in the state, according to the executive summary, and coastal communities can use it for risk management and adaptation planning.
Sea level rise is a concern because of the importance of shoreline areas economically, culturally and environmentally as well as the presence of waterfront infrastructure, particularly in communities such as La Conner and Anacortes.
Sea level rise is occurring as a result of global climate change as warming ocean waters expand and ice melts.
Statewide, sea level is likely to rise about 1.5 feet by 2100 or, in a less likely scenario, as much as 7 feet by 2100, according to the new study.
The difference between the two projections depends on how well the world reduces greenhouse gas emissions, how rapidly polar ice melts and other factors.
Whether greenhouse gas emissions are reduced makes more of a difference in potential sea level rise as time progresses, with the gap between projections increasing from about 1 inch by 2050 to about 11 inches by 2150, according to the study.
The study also includes what is believed to be the absolute limit of sea level rise.
Statewide, sea level rise is not expected to exceed about 8.3 feet by 2100, or 18.3 feet by 2150, according to the study.
For Skagit County shorelines, the limit to sea level rise is an estimated 8.4 feet on average, according to the study data.
Guillaume Mauger, a research scientist at the University of Washington’s Climate Impacts Group and a co-author of the study, said communities can use the information in the study to decide how to protect waterfront infrastructure such as La Conner’s Main Street businesses and Anacortes’ Cap Sante Marina.
Coastal floods are already an issue along much of the marine shoreline in Skagit County, Mauger said, and sea level rise will make that flooding worse.
The new study may help Skagit County leaders hone in on risks specific to local shorelines.
Ian Miller, a coastal hazards specialist at Washington Sea Grant and lead author of the study, said the hope is that the new sea level rise projections can be used for community level analysis and planning.
The new study comes a decade after the first such Climate Impacts Group report and builds off of a national report for Washington, Oregon and California that was published in 2012, according to a news release.
In comparison to those earlier studies, the new one takes a close look at the state’s shorelines and how they are affected by geology-driven land motion, study co-author Harriet Morgan said in a news release.
Areas of the Olympic Peninsula are lifting and areas around south Puget Sound are sinking, according to the study.
Miller said that movement is in response to the former weight of ice masses that have long melted, as well as in response to the movement of tectonic plates such as along the Cascadia Subduction Zone beneath the Pacific Ocean.
Study authors said it’s important for communities affected by that land movement to be aware of how it may interact with sea level rise.
The new study was led by Washington Sea Grant and the University of Washington’s Climate Impacts Group. University of Oregon and U.S. Geological Survey scientists were also involved.
The study was largely funded by the National Oceanic and Atmospheric Administration along with support from other federal, state and local organizations including the Padilla Bay National Estuary Research Reserve.