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sábado, 19 de septiembre de 2015

NASA : Watching Rising Seas From Space .- Observación de crecimiento de los mares desde el Espacio


This video describes the causes of sea level rise and how sea level has changed over the last two decades as observed by the Jason series of satellite missions.
Credits: NASA/JPL

NASA Science Zeros in on Ocean Rise: How Much? How Soon?

Seas around the world have risen an average of nearly 3 inches since 1992, with some locations rising more than 9 inches due to natural variation, according to the latest satellite measurements from NASA and its partners. An intensive research effort now underway, aided by NASA observations and analysis, points to an unavoidable rise of several feet in the future.

Members of NASA’s new interdisciplinary Sea Level Change Team will discuss recent findings and new agency research efforts during a media teleconference today at 12:30 p.m. EDT. NASA will stream the teleconference live online.

The question scientists are grappling with is how quickly will seas rise?

“Given what we know now about how the ocean expands as it warms and how ice sheets and glaciers are adding water to the seas, it’s pretty certain we are locked into at least 3 feet of sea level rise, and probably more,” said Steve Nerem of the University of Colorado, Boulder, and lead of the Sea Level Change Team. “But we don't know whether it will happen within a century or somewhat longer.”

Team scientists will discuss a new visualization based on 23 years of sea level data – the entire record of available satellite data -- which reveals changes are anything but uniform around the globe. The record is based on data from three consecutive satellite missions, the first a collaboration between NASA and the French space agency, Centre National d'Études Spatiales, launched in 1992. The next in the series is Jason-3, led by the National Oceanic and Atmospheric Administration (NOAA) with participation by NASA, CNES and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).
 

In 2013, the United Nations Intergovernmental Panel on Climate Change (IPCC) issued an assessment based on a consensus of international researchers that stated global sea levels would likely rise from 1 to 3 feet by the end of the century. According to Nerem, new research available since this report suggests the higher end of that range is more likely, and the question remains how that range might shift upward.

The data reveal the height of the sea surface is not rising uniformly everywhere. Regional differences in sea level rise are dominated by the effects of ocean currents and natural cycles such as the Pacific Decadal Oscillation (PDO). But, as these natural cycles wax and wane, they can have major impacts on local coastlines.

“Sea level along the west coast of the United States has actually fallen over the past 20 years because long-term natural cycles there are hiding the impact of global warming,” said Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “However, there are signs this pattern is changing. We can expect accelerated rates of sea level rise along this coast over the next decade as the region recovers from its temporary sea level ‘deficit.’”

Scientists estimate that about one-third of sea level rise is caused by expansion of warmer ocean water, one-third is due to ice loss from the massive Greenland and Antarctic ice sheets, and the remaining third results from melting mountain glaciers. But, the fate of the polar ice sheets could change that ratio and produce more rapid increases in the coming decades.
GRACE consists of twin co-orbiting satellites that fly in a near polar orbit separated by a distance of 220 km. GRACE precisely measures the distance between the two spacecraft in order to make detailed measurements of the Earth's gravitational field. Since its launch in 2002, GRACE has provided a continuous record of changes in the mass of the Earth's ice sheets.
Credits: NASA Goddard's Scientific Visualization Studio
 
The Greenland ice sheet, covering 660,000 square miles -- nearly the area of Alaska -- shed an average of 303 gigatons of ice a year over the past decade, according to satellite measurements. The Antarctic ice sheet, covering 5.4 million square miles --larger than the United States and India combined -- has lost an average of 118 gigatons a year.

“We’ve seen from the paleoclimate record that sea level rise of as much as 10 feet in a century or two is possible, if the ice sheets fall apart rapidly,” said Tom Wagner, the cryosphere program scientist at NASA Headquarters in Washington. “We’re seeing evidence that the ice sheets are waking up, but we need to understand them better before we can say we’re in a new era of rapid ice loss.”

Although Antarctica’s contribution to sea level rise currently is much smaller than that of Greenland, recent research indicates this could change in the upcoming century. In 2014, two West Antarctica studies focused on the acceleration of the glaciers in the Amundsen Sea sector showed its collapse is underway.

East Antarctica’s massive ice sheet remains the primary unknown in sea level rise projections. Though it appears to be stable, a recent study found under a major glacier two deep troughs that could draw warm ocean water to the base of the glacier, causing it to melt.

“The prevailing view among specialists has been that East Antarctica is stable, but we don’t really know,” said glaciologist Eric Rignot of the University of California Irvine and JPL. “Some of the signs we see in the satellite data right now are red flags that these glaciers might not be as stable as we once thought. There’s always a lot of attention on the changes we see now, but as scientists our priority needs to be on what the changes could be tomorrow.”

One of the keys to understanding future rates of ice loss is determining the role ocean currents and ocean temperatures play in melting the ice sheets from below its edges. A new six-year NASA field campaign took to the waters around Greenland this summer to probe how warming ocean waters are triggering Greenland glacier degradation. The Oceans Melting Greenland (OMG) project is taking coastal ocean temperature measurements, observing glacial thinning at the ice’s edge, and producing the first high-resolution maps of the seafloor, fjords and canyons in the continental shelf surrounding Greenland.

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives, and safeguard our future. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.
 
La capa de hielo de Groenlandia, que cubre 660.000 millas cuadradas - casi el área de Alaska - arrojar un promedio de 303 gigatoneladas del hielo al año en la última década, de acuerdo con las mediciones por satélite. La capa de hielo de la Antártida, que cubre 5,4 millones de millas cuadradas --larger que Estados Unidos y la India combinado - ha perdido un promedio de 118 gigatoneladas al año.

"Hemos visto a partir del registro paleoclima que el ascenso del nivel del mar de hasta 10 pies en un siglo o dos es posible, si las capas de hielo se deshacen rápidamente", dijo Tom Wagner, el científico del programa criosfera de la NASA en Washington. "Estamos viendo evidencia de que las capas de hielo se están despertando, pero tenemos que entenderlos mejor antes de que podamos decir que estamos en una nueva era de la pérdida de hielo rápida."

Aunque la contribución de la Antártida al aumento del nivel del mar en la actualidad es mucho más pequeña que la de Groenlandia, investigaciones recientes indican que esto podría cambiar en el siglo próximo. En 2014, dos estudios Antártida Occidental se centraron en la aceleración de los glaciares en el sector del mar de Amundsen mostraron su colapso está en marcha.

Capa de hielo de la Antártida oriental masiva sigue siendo el desconocido primaria en las proyecciones de aumento del nivel del mar. A pesar de que parece ser estable, un estudio reciente encontró bajo una de las principales dos glaciar valles profundos que podrían extraer agua caliente del océano a la base del glaciar, haciendo que se derrita.

"La opinión predominante entre los especialistas ha sido que este de la Antártida es estable, pero no se sabe muy bien", dijo el glaciólogo Eric Rignot, de la Universidad de California en Irvine y el JPL. "Algunos de los signos que vemos en los datos de los satélites ahora son banderas rojas que estos glaciares podrían no ser tan estable como lo que se pensaba. Siempre hay una gran cantidad de atención en los cambios que vemos ahora, pero como científicos nuestra prioridad tiene que ser en lo que los cambios podrían ser mañana. "

Una de las claves para la comprensión de las futuras tasas de pérdida de hielo es determinar el papel las corrientes oceánicas y las temperaturas oceánicas desempeñan en la fusión de las capas de hielo de debajo de sus bordes. Un nuevo seis años campaña de campo de la NASA llevó a las aguas alrededor de Groenlandia este verano para sondear cómo el calentamiento aguas oceánicas están provocando la degradación de los glaciares de Groenlandia. Los Océanos proyecto Groenlandia (OMG) de fusión está tomando medidas de la temperatura del océano costero, observando el adelgazamiento de los glaciares en la orilla del hielo, y la producción de los primeros mapas de alta resolución del fondo del mar, fiordos y cañones en la plataforma continental que rodea Groenlandia.

La NASA utiliza el punto de vista del espacio para aumentar nuestra comprensión de nuestro planeta, mejorar la vida y salvaguardar nuestro futuro. NASA desarrolla nuevas maneras de observar y estudiar los sistemas naturales interconectados de la Tierra con los registros de datos a largo plazo. La agencia comparte libremente este conocimiento único y trabaja con instituciones de todo el mundo para obtener nuevos conocimientos sobre cómo nuestro planeta está cambiando.Imágenes y vídeo de apoyo a la teleconferencia de hoy están disponibles en:http://go.nasa.gov/risingseasbriefing
Más información sobre la investigación de la NASA en un cambio en el nivel del mar:http://www.nasa.gov/risingseas
Para obtener más información sobre las actividades de ciencias de la Tierra de la NASA, visite:http://www.nasa.gov/earth
Steve Cole
 
Sede, Washington
 
202-358-0918stephen.e.cole@nasa.gov

Última actualización: 26 de agosto 2015
Editor: Karen NorthonEtiquetas: clima, Tierra, Agua
 
Images and video supporting the media teleconference today are available at:


Learn more about NASA's research into sea level change at:

For more information on NASA’s Earth science activities, visit:


-end-
Steve Cole
Headquarters, Washington
202-358-0918
stephen.e.cole@nasa.gov
Last Updated: Aug. 26, 2015
Editor: Karen Northon
Tags:  Climate, Earth, Water,
NASA
Guillermo Gonzalo Sánchez Achutegui