Sea Level Rise

New research by top climate scientists suggests that global sea level rise could accelerate much faster than previously predicted. The lead author in this work is Dr. James Hansen, who in 1981 published research in the journal Science that foresaw human-caused global warming. Hansen, former head of the NASA Goddard Institute for Space Studies in New York City, is renowned for his early (1980s) science-based insistence that global warming trends could be attributed to human causes in addition to natural variation. In 1988, Hansen testified to this effect before a U.S. Congressional committee, a bold move for the time.

Now cutting edge research from Hansen and others is telling us that we could see several meters of sea level rise over the next 50 to 150 years because feedback mechanisms caused by melting ice in Greenland and Antarctica are amplifying and accelerating the melt. Making sense of paleoclimate data (evidence of the earth’s past climate going back hundreds to millions of years) is part of what’s behind these new models and projections. (Dr. Hansen describes his work in this YouTube video.)

Sea level is rising now – it’s not just in the future. The speed at which this is happening is becoming much better defined given advances in technology and increasingly global coverage of gauges. As governments and scientists develop tools to better measure changes as they occur, models and projections are revised (Figure 1). As recently as February 2017, the U.S. National Oceanic and Atmospheric Administration (NOAA) increased its projections of global sea level rise, estimating that by the year 2100, global sea levels could rise between 0.35 metres (one foot) and 2.5 metres (8.2 feet). The estimates range because different climate scenarios make different assumptions about what efforts will be made to reduce harmful carbon emissions that cause global warming and rising seas. Just a decade ago, projections for 2100 topped out at 0.6 metres, so the 2017 projection of up to 2.5  metres  is a significant change (Figure 1).

Figure 1. Projections of sea level rise vary depending on who publishes them, as they present the scientific consensus of different groups. Both the low end and high end of projections are increasing as scientists learn more about how global climate systems work. Here, estimates of the Intergovernmental Panel on Climate Change (IPCC) and the U.S. National Oceanic and Atmospheric Administration (NOAA) are shown. Projections published in 2012, 2013, and 2017 do take melting ice sheets into account. These projections are anchored in 1980 1999, 1992, 1986- 2005, and 2000, respectively. Sources: IPCC 2007; NOAA 2012; IPCC 2013; NOAA 2017.

Why have projections increased?

New insights about the Antarctic and Greenland ice shelves  suggest they are melting from underneath, where they meet a warming sea, as well as on the surface (Figure 2). Forecasting sea level rise is far from simple and projections have large uncertainties associated with them, but as scientists learn more about the feedback mechanisms, the projected magnitude of sea level rise increases, as does the uncertainty and range of possible values (Figure 1).

Figure 2. Source: figure adapted from Hansen et al 2016, Figure 18, CC-BY.

The impacts of rising sea levels range from major changes to our nearshore marine habitats and food webs, to catastrophic flooding that will affect millions of coastal residents globally by late this century. In B.C., coastal erosion will increase (Figure 3) and anticipated loss of wetland habitat would impact salmon, coastal birds, forage fish, and other coastal species. Approximately 80 percent of B.C.’s population resides in coastal communities and many of our commercially traded goods arrive through critical infrastructure (i.e.,airports, ports and ferry terminals) that line our shores and are at risk of flooding (Figure 4). The general risks that climate change and rising seas present to different regions of Canada’s west coast are summarized in a 2016 report, Canada’s Marine Coasts in a Changing Climate, published by the Government of Canada.

Figure 3. Signs of erosion along the coastal bluff on Denman Island on Nov. 17, 2012 during a king tide. (Photo: JohnMac2011, Flickr, CC BY-NC 2.0)

Figure 4. Road infrastructure at risk during high king tide plus storm surge, Nov. 24, 2011 in Colwood, near Victoria, B.C. (Photo: Tina Neale, Flickr, CC BY-NC-SA 2.0)

Coastal First Nations are especially vulnerable to impacts of sea level rise including flooding and erosion. Harvesting of traditional seafood is often a coastal activity. While specific impacts to nearshore resources are hard to predict, they will very likely affect the availability of traditional food sources, particularly where armoring and steep shorelines limit shore migration and where substrates will be modified (e.g., winnowed or coarsened). In addition, a large number of cultural and archaeological sites sit in coastal areas and at low elevations. The impacts are already being felt, as waters from a high king tide in 2012 covered a unique cultural feature, called the Man Who Fell from Heaven, in Metlakatla Pass on the North Coast and rose alarmingly close to the Elders housing unit there (Figure 5). First Nations and archaeologists continue to identify new cultural sites and make discoveries that document the history of occupation and use of the B.C. coast. The urgency around this work increases as ocean levels rise.

Figure 5. Left: The Man Who Fell From Heaven is the most important and well-known cultural feature in Metlakatla Pass; it is under approximately three feet of water in this photo taken Dec. 12, 2012. Right: Elders Unit in Metlakatla, B.C. Dec 12, 2012. (Photos: Metlakatla Guardians, Flickr, CC BY-NC-SA 2.0)

One area of the coast experiencing dramatic change in recent years is the northeast coast of Haida Gwaii where the sandy bluffs are retreating at a rate of up to 12 metres annually (Figure 6).

Figure 6. Receding bluffs in Naikoon Provincial Park, Northeast Graham Island, Haida Gwaii. (Photo: Christine Rondeau, Flickr, CC BY 2.0)

The Pacific Coast of North America has experienced relatively little sea level change since 1992 compared to some other coastlines around the world, according to satellite altimetry data from NOAA (Figure 7). Tide gauge data for stations with long records at Seattle, San Francisco, and San Diego shows trends that vary over decades due to Pacific Ocean circulation patterns including the Pacific Decadal Oscillation (PDO) and the annual El Niño Southern Oscillation (ENSO). These data show a period of slow sea level rise from 1900 to 1930, then faster rise mid-century between 1930 and 1980, and slow again until about 2005 (see Figure 1 in Bromirski et al 2011). However, follow-up work has identified a recent and significant increase in sea level along the West Coast of North America (i.e., 10 centimetres rise between 2012 and 2016) and suggests that trends for our coast are now closer to the global average of 3.3 millimetres per year when the influence of regional circulation patterns are removed. Further, this faster rate of rise will likely persist in the coming years.

Figure 7. Magnitude of sea level change observed between 1992 and 2016. Source: NOAA’s Laboratory for satellite imagery.

In 2014, Natural Resources Canada (NRCan) published projections of sea level rise for 19 locations along the B.C. coast (Figure 8). These projections are dated and possibly conservative as they were released prior to recent discoveries concerning ice sheet melt, feedback mechanisms, and the recent shift in the Pacific Ocean region.

Figure 8. Projected sea level rise by 2100, relative to 1995, for 19 B.C. coastal locations. These projections are based on the IPCC 2013 extreme scenario and GPS observations of vertical land motion, with an added 0.65 metres of global sea level rise anticipated from West Antarctic Ice Sheet loss. Note that NOAA’s 2017 projections suggest that these projections, considered extreme in 2014, are now conservative. Source: Natural Resources Canada, 2014.

Natural Resources Canada also developed an index of sensitivity to sea level rise, and scored Canada’s coastlines based in the degree to which a coastline may experience physical changes such as flooding, erosion, beach migration, and coastal dune destabilization. In the 2009 analysis, Atlantic Canada and parts of the Beaufort Sea coast were identified as major regions of high sensitivity. Small areas of high sensitivity occur in B.C. (Figure 9). The index is currently being updated. A gap in our knowledge currently exists as to the localized effects of global sea level rise for the B.C. coast, taking into account vertical land motions and recent changes in the regional rates of sea level rise. Research to model and communicate these localized effects, such as the U.S. Geological Survey is undertaking for the U.S. Pacific and Arctic coasts, would be a valued contribution.

Figure 9. Areas in red were identified as highly sensitive to sea level rise in a 2009 analysis. Source: Natural Resources Canada.

Individual and Organization Actions:

• Inquire about your community’s planning for sea level rise. Make sure it is happening, get involved, learn the risks, and voice your opinions.
• Spread the word that sea level rise is happening and we need to acknowledge and plan.
• Support or engage in studies to improve our understanding of how coastal impacts are going to affect ecosystem services people depend upon.
• Reduce your greenhouse gas emissions:
  • Reduce your carbon footprint
  • Insulate your home, check for drafts, lower your thermostat in the winter
  • Consider an electric vehicle, car share, take transit or propel yourself
  • Wash clothing in cool water and hang your clothes to dry
  • For more tips see BC Hydro Power Smart
• Adopt green policies and practices within your organization.
• Raise awareness by continuing to post photos of king tides on social media using KingTidesBC and #KingTides.

Government Actions and Policy:

• Work urgently to eliminate fossil fuel emissions, a major driver of climate change.
• Update federal sea level rise projections more frequently as climate science advances.
• Update provincial policy guidelines more frequently as climate science advances.
• Develop policies to limit development of critical infrastructure in projected flood zones.
• Support or engage in studies to improve our understanding of how coastal impacts are going to affect ecosystem services people depend upon.
• Communicate sea level rise projections and government policies and guidelines to Canadians.
• Begin planning for retreat of key facilities and infrastructure from high flood hazard areas at the end of their
  service life.