NEWS NOTES ON SUSTAINABLE WATER RESOURCES Sea Level Changes Changes in sea level could lead to major impacts on the land. For example, here is a case in which the erosion rate of coastal cliffs would greatly increase: https://www.usgs.gov/news/sea-level-rise-could-double-erosion-rates-southern-california-coastal-cliffsU.S. Geological Survey scientists combined several computer models for the first time to forecast cliff erosion along the Southern California coast. Their peer-reviewed study was published in a recent issue of the American Geophysical Union’s Journal of Geophysical Research - Earth Surface. The research also showed that for sea-level rise scenarios ranging from about 1.5 feet to 6.6 feet by 2100, bluff tops along nearly 300 miles of Southern California coasts could lose an average of 62 to 135 feet by 2100 – and much more in some areas.A closer look at the problem reveals that sea level changes can be connected to climate change. Global sea level and the Earth's climate are closely linked. The Earth's climate has warmed about 1°C (1.8°F) during the last 100 years. As the climate has warmed following the end of a recent cold period known as the "Little Ice Age" in the 19th century, sea level has been rising about 1 to 2 millimeters per year due to the reduction in volume of ice caps, ice fields, and mountain glaciers in addition to the thermal expansion of ocean water.Climate-related sea-level changes of the last century are very minor compared with the large changes in sea level that occur as climate oscillates between the cold and warm intervals that are part of the Earth's natural cycle of long-term climate change.During cold-climate intervals, known as glacial epochs or ice ages, sea level falls because of a shift in the global hydrologic cycle: water is evaporated from the oceans and stored on the continents as large ice sheets and expanded ice caps, ice fields, and mountain glaciers. Global sea level was about 125 meters below today's sea level at the last glacial maximum about 20,000 years ago (Fairbanks, 1989). As the climate warmed, sea level rose because the melting North American, Eurasian, South American, Greenland, and Antarctic ice sheets returned their stored water to the world's oceans. During the warmest intervals, called interglacial epochs, sea level is at its highest. Today we are living in the most recent interglacial, an interval that started about 10,000 years ago and is called the Holocene Epoch by geologists.A more complete discussion of this phenomenon can be found here:https://www.usgs.gov/special-topic/water-science-school/science/sea-level-and-climate?qt-science_center_objects=0#qt-science_center_objects ; No matter what the cause may be, changes in sea level could cause impacts on current land uses that are far greater than any in the past. Action to address potential problems therefore becomes an important consideration. The Sea-Level Rise Hazards and Decision-Support project assesses present and future coastal vulnerability to provide actionable information for management of our Nation’s coasts. Through multidisciplinary research and collaborative partnerships with decision-makers, physical, biological, and social factors that describe landscape and habitat changes are incorporated in a probabilistic modeling framework to explore the future likelihood of a variety of impacts and outcomes. Scenario-based products and tools can be applied to inform adaptation strategies, evaluate tradeoffs, and examine mitigation options Advanced decision-support methods are required to provide technical expertise to those decision makers who must take action in such cases. More information about this aspect of the problem can be found here: https://www.usgs.gov/centers/whcmsc/science/sea-level-rise-hazards-and-decision-support-0?qt-science_center_objects=0#qt-science_center_objects ; In general, problems might be expected to occur in land loss from inundation and erosion, migration of coastal landforms, changes to groundwater systems, and changes to coastal habitat.