page_title: Sea level
section_title: Short-term and periodic changes
hierarchical_section_title: Sea level / Change / Short-term and periodic changes
caption_attribution_description: Calving front of the Upsala Glacier (Argentina). This glacier has been thinning and retreating at a rapid rate during the last decades – from 2006 to 2010, it receded 43.7 yards (40 meters) per year. During summer 2012, large calving events prevented boat access to the glacier. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Etienne Berthier, Université de Toulouse NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
context_page_description: Mean sea level is an average level of the surface of one or more of Earth's bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.
  Sea levels can be affected by many factors and are known to have varied greatly over geological time scales. However, 20th century and current millennium sea level rise is presumed to be caused by global warming, and careful measurement of variations in MSL can offer insights into ongoing climate change.
  The term above sea level generally refers to above mean sea level. The term APSL means Above Present Sea Level, comparing sea levels in the past with the level today.
context_section_description: There are many factors which can produce short-term (a few minutes to 14 months) changes in sea level. Two major mechanisms are causing sea level to rise. First, shrinking land ice, such as mountain glaciers and polar ice sheets, is releasing water into the oceans. Second, as ocean temperatures rise, the warmer water expands.
caption: Melting glaciers are causing a change in sea level
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