San Diego’s Vulnerability to Sea Level Rise Dan Cayan Scripps Institution of Oceanography, UC San Diego and USGS North County (San Diego) Climate Change Alliance Encinitas, CA 22 Oct 2015 Sponsors: California Energy Commission NOAA RISA program “CNAP” USGS CASCADE study Southwest Climate Science Center

96.5% of Earth's water resides in the oceans 321 Million cubic miles of water in the oceans (96.5%) 11.5 Million cubic miles of water on land ( 3.5%) 5.8 Million cubic miles of water in ice 2’ of sea level rise from glaciers and ice sheets would add cubic miles of water to the oceans (an increase of.016%), and subtract cubic miles of water (ice) from land (a decrease of about 0.4%) 96.5% of Earth's water resides in the oceans 321 Million cubic miles of water in the oceans (96.5%) 11.5 Million cubic miles of water on land ( 3.5%) 5.8 Million cubic miles of water in ice 2’ of sea level rise from glaciers and ice sheets would add cubic miles of water to the oceans (an increase of.016%), and subtract cubic miles of water (ice) from land (a decrease of about 0.4%) Presently, 10% of land area on Earth is covered with glacial ice, including glaciers, ice caps, and the ice sheets of Greenland and Antarctica. These areas are 15M km**2 = 5.8M mile**2. During the maximum point of the last ice age, glaciers covered about 32% of total land area. Glaciers store more than 50% of the world's freshwater. From the 17th century to the late 19th century, the world experienced a “Little Ice Age,” when temperatures were cool enough for glaciers to advance in many areas of the world. In the United States, glaciers cover over 75,000 square kilometers (30,000 square miles). Most US glaciers are located in Alaska, but a few are still found in mountains of California

since last glaciation

Source: IPCC TAR 2001 Although these are relatively low concentrations, increases in these trace gases cause more terrestrial infrared radiation to be absorbed, thus warming the atmosphere, the earth’s surface and the oceans. Greenhouse Gases increasing rapidly Humans have altered the atmospheric composition during the industrial era

More Energy Coming In than Going Out Energy Imbalance estimated at 0.58 watts/m**2 (Hansen 2012) When the Earth is in energy imbalance, with more energy coming in than radiating back out into space, we experience global warming. This can be determined empirically in two ways. Firstly, by using satellites to directly measure the difference between incoming energy from the sun and outgoing radiation from the earth. Secondly, by adding up the energy content of the atmosphere and ocean over time. (Murphy 2009) does both.

Warming of the Earth’s surface recently and projected Departures in temperature in o C (from the 1990 value) ProxyInstrument Projections oFoF oCoC

Components of Global and Regional Sea-Level Rise Sea level at a particular place can be higher or lower than the global mean due to regional effects recent ( ) Sea Level Rise thermal Expansion 0.6 mm/yr Ice melt (glaciers, ice sheets) 1.8 mm/yr

Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future—NRC Committee findings from a presentation by Dr. Robert A. Dalrymple, Chair, NRC West Coast SLR Committee Johns Hopkins University

Global sea-level is rising primarily because land ice is melting and ocean water expands as it warms. 1.7 mm per year over 20 th century (from tide gages) 3.1 mm per year since 1993 (from satellites & tide gages)

Global sea-level is rising primarily because land ice is melting and ocean water expands as it warms. 1.7 mm per year over 20 th century (from tide gages) 3.1 mm per year since 1993 (from satellites & tide gages) Sea-level is projected to rise at higher rates in the future

Regional and Global Sea- Level Rise Projections Being used by California for interim planning 11

during high sea levels, the sea is often not quiescent January 1983 Monterey Bay, California

GREATEST PROBLEMS: LARGE STORM + HIGH TIDE Very high sea levels during the massive January storm GREATEST PROBLEMS: LARGE STORM + HIGH TIDE Very high sea levels during the massive January storm highest sea level historically along much of California Coast

Extreme sea level occurrences La Jolla observed at or above 99.99% historical hourly threshold 1.41m above mean Extreme sea level occurrences La Jolla observed at or above 99.99% historical hourly threshold 1.41m above mean Highest sea levels have mainly occurred in just a few years, esp large El Niños (e.g., 1983) Highest sea levels have mainly occurred in just a few years, esp large El Niños (e.g., 1983) 1983

during high sea levels, the sea is often not quiescent January 1983 Monterey Bay, California

Wave Power Calif Coast

as mean sea level rises, projections indicate a marked increase in the likelihood of exceeding historical extreme levels projected sea level modeled number of hours above 99.99% historical level

since 1993 : no sea level rise in eastern Pacific along California coast and much sea level rise in western Pacific, probably owing to wind patterns but, during last 2 yrs, eastern Pacific coast has begun to rise again ….. will this continue?

Global SST Departures ( o C) During the Last Four Weeks During the last four weeks, equatorial SSTs were above average across the central and eastern Pacific and most of the Indian Ocean. SSTs were below average in the eastern Atlantic Ocean and near Indonesia. Very warm surface waters now in Eastern Pacific

Tracking El Niño 2015

Conclusions Sea-level in California (south of Cape Mendocino) is expected to rise considerably by 2100, about the same as global sea-level rise. There is a wide range of estimates of SLR (1’ to more than 6’ by 2100) because the amount of ice melt from Antarctica and Greenland is uncertain. Sea-level rise will magnify the adverse impact of storm surges and high waves on the coast. Greatest problems will likely occur when large winter storm coincides with high tide. Historically, highest sea level and wave events have happened preferentially in El Niño years. A large El Niño that developed in spring and summer 2015 is likely to persist through winter