Zeno Swijtink
07-15-2010, 09:56 AM
Indian Ocean Sea Level Rise Threatens Coastal Areas (https://www.newswise.com/articles/indian-ocean-sea-level-rise-threatens-coastal-areas)
National Center for Atmospheric Research (NCAR)
Source: Nature Geoscience, July 11, 2010
Indian Ocean sea levels are rising unevenly and threatening residents in some densely populated coastal areas and islands, a new study concludes. The study, led by scientists at the University of Colorado at Boulder (CU) and the National Center for Atmospheric Research (NCAR), finds that the sea level rise is at least partly a result of climate change.
Sea level rise is particularly high along the coastlines of the Bay of Bengal, the Arabian Sea, Sri Lanka, Sumatra and Java, the authors found. The rise-which may aggravate monsoon flooding in Bangladesh and India-could have future impacts on both regional and global climate.
The key player in the process is the Indo-Pacific warm pool, an enormous, bathtub-shaped area spanning a region of the tropical oceans from the east coast of Africa to the International Date Line in the Pacific. The warm pool has heated by about 1 degree Fahrenheit, or 0.5 degrees Celsius, in the past 50 years, primarily because of human-generated emissions in greenhouses gases.
"Our results from this study imply that if future anthropogenic warming effects in the Indo-Pacific warm pool dominate natural variability, mid-ocean islands such as the Mascarenhas Archipelago, coasts of Indonesia, Sumatra, and the north Indian Ocean may experience significantly more sea level rise than the global average," says lead author Weiqing Han of CU's atmospheric and oceanic sciences department.
While a number of areas in the Indian Ocean region are experiencing sea level rise, sea level is lowering in other areas. The study indicated that the Seychelles Islands and Zanzibar off Tanzania's coast show the largest sea level drop.
"Global sea level patterns are not geographically uniform," says NCAR scientist Gerald Meehl, a co-author. "Sea level rise in some areas correlates with sea level fall in other areas."
Indian Ocean sea levels are rising unevenly and threatening residents in some densely populated coastal areas and islands, a new study concludes. The study, published in Nature Geoscience, finds that the sea level rise is at least partly a result of climate change.
https://www.newswise.com/images/uploads/2010/07/14/climatology_composite.jpg
Image courtesy NASA Earth Observatory.
A new study in Nature Geoscience finds that Indian Ocean sea levels are rising unevenly and threatening residents in some densely populated coastal areas, particularly those along the Bay of Bengal, the Arabian Sea, Sri Lanka, Sumatra, and Java. This image shows the key player in the process, the Indo-Pacific warm pool, in bright orange. This enormous, bathtub-shaped area spans a region of the tropical oceans from the east coast of Africa to the International Date Line in the Pacific. The warm pool has heated by about 1 degree Fahrenheit, or 0.5 degrees Celsius, in the past 50 years, primarily because of human-generated emissions of greenhouses gases.
The patterns of sea level change are driven by the combined enhancement of two primary atmospheric wind patterns known as the Hadley circulation and the Walker circulation. The Hadley circulation in the Indian Ocean is dominated by air currents rising above strongly heated tropical waters near the equator and flowing poleward at upper levels, then sinking to the ocean in the subtropics and causing surface air to flow back toward the equator.
The Indian Ocean's Walker circulation causes air to rise and flow westward at upper levels, sink to the surface and then flow eastward back toward the Indo-Pacific warm pool.
"The combined enhancement of the Hadley and Walker circulation forms a distinct surface wind pattern that drives specific sea level patterns," Han says.
In their Nature Geoscience article, the authors write, "Our new results show that human-caused changes of atmospheric and oceanic circulation over the Indian Ocean region-which have not been studied previously-are the major cause for the regional variability of sea level change."
The new study indicates that in order to anticipate global sea level change, researchers also need to know the specifics of regional sea level changes.
"It is important for us to understand the regional changes of the sea level, which will have effects on coastal and island regions," says NCAR scientist Aixue Hu.
The research team used several sophisticated ocean and climate models for the study, including the Parallel Ocean Program-the ocean component of the widely used Community Climate System Model, which is supported by NCAR and DOE. In addition, the team used a wind driven, linear ocean model for the study.
The complex circulation patterns in the Indian Ocean may also affect precipitation by forcing even more atmospheric air than normal down to the surface in Indian Ocean subtropical regions, Han speculates.
"This may favor a weakening of atmospheric convection in subtropics, which may increase rainfall in the eastern tropical regions of the Indian Ocean and drought in the western equatorial Indian Ocean region, including east Africa," Han says.
National Center for Atmospheric Research (NCAR)
Source: Nature Geoscience, July 11, 2010
Indian Ocean sea levels are rising unevenly and threatening residents in some densely populated coastal areas and islands, a new study concludes. The study, led by scientists at the University of Colorado at Boulder (CU) and the National Center for Atmospheric Research (NCAR), finds that the sea level rise is at least partly a result of climate change.
Sea level rise is particularly high along the coastlines of the Bay of Bengal, the Arabian Sea, Sri Lanka, Sumatra and Java, the authors found. The rise-which may aggravate monsoon flooding in Bangladesh and India-could have future impacts on both regional and global climate.
The key player in the process is the Indo-Pacific warm pool, an enormous, bathtub-shaped area spanning a region of the tropical oceans from the east coast of Africa to the International Date Line in the Pacific. The warm pool has heated by about 1 degree Fahrenheit, or 0.5 degrees Celsius, in the past 50 years, primarily because of human-generated emissions in greenhouses gases.
"Our results from this study imply that if future anthropogenic warming effects in the Indo-Pacific warm pool dominate natural variability, mid-ocean islands such as the Mascarenhas Archipelago, coasts of Indonesia, Sumatra, and the north Indian Ocean may experience significantly more sea level rise than the global average," says lead author Weiqing Han of CU's atmospheric and oceanic sciences department.
While a number of areas in the Indian Ocean region are experiencing sea level rise, sea level is lowering in other areas. The study indicated that the Seychelles Islands and Zanzibar off Tanzania's coast show the largest sea level drop.
"Global sea level patterns are not geographically uniform," says NCAR scientist Gerald Meehl, a co-author. "Sea level rise in some areas correlates with sea level fall in other areas."
Indian Ocean sea levels are rising unevenly and threatening residents in some densely populated coastal areas and islands, a new study concludes. The study, published in Nature Geoscience, finds that the sea level rise is at least partly a result of climate change.
https://www.newswise.com/images/uploads/2010/07/14/climatology_composite.jpg
Image courtesy NASA Earth Observatory.
A new study in Nature Geoscience finds that Indian Ocean sea levels are rising unevenly and threatening residents in some densely populated coastal areas, particularly those along the Bay of Bengal, the Arabian Sea, Sri Lanka, Sumatra, and Java. This image shows the key player in the process, the Indo-Pacific warm pool, in bright orange. This enormous, bathtub-shaped area spans a region of the tropical oceans from the east coast of Africa to the International Date Line in the Pacific. The warm pool has heated by about 1 degree Fahrenheit, or 0.5 degrees Celsius, in the past 50 years, primarily because of human-generated emissions of greenhouses gases.
The patterns of sea level change are driven by the combined enhancement of two primary atmospheric wind patterns known as the Hadley circulation and the Walker circulation. The Hadley circulation in the Indian Ocean is dominated by air currents rising above strongly heated tropical waters near the equator and flowing poleward at upper levels, then sinking to the ocean in the subtropics and causing surface air to flow back toward the equator.
The Indian Ocean's Walker circulation causes air to rise and flow westward at upper levels, sink to the surface and then flow eastward back toward the Indo-Pacific warm pool.
"The combined enhancement of the Hadley and Walker circulation forms a distinct surface wind pattern that drives specific sea level patterns," Han says.
In their Nature Geoscience article, the authors write, "Our new results show that human-caused changes of atmospheric and oceanic circulation over the Indian Ocean region-which have not been studied previously-are the major cause for the regional variability of sea level change."
The new study indicates that in order to anticipate global sea level change, researchers also need to know the specifics of regional sea level changes.
"It is important for us to understand the regional changes of the sea level, which will have effects on coastal and island regions," says NCAR scientist Aixue Hu.
The research team used several sophisticated ocean and climate models for the study, including the Parallel Ocean Program-the ocean component of the widely used Community Climate System Model, which is supported by NCAR and DOE. In addition, the team used a wind driven, linear ocean model for the study.
The complex circulation patterns in the Indian Ocean may also affect precipitation by forcing even more atmospheric air than normal down to the surface in Indian Ocean subtropical regions, Han speculates.
"This may favor a weakening of atmospheric convection in subtropics, which may increase rainfall in the eastern tropical regions of the Indian Ocean and drought in the western equatorial Indian Ocean region, including east Africa," Han says.