sea-level rise, future impact & possible solutions
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Sea-Level Rise, Future Impact & Possible Solutions . Anastasia Tsitali. Environmental Physics. Causes. Global Warming. concentration of greenhouse gases (burning fossil fuel, deforestation ..) global dimming (aerosols in the atmosphere). - PowerPoint PPT PresentationTRANSCRIPT
Sea-Level Rise, Future Impact & Possible Solutions
Anastasia TsitaliEnvironmental Physics
Global Warming
Effects
Causes• concentration of greenhouse gases (burning fossil fuel, deforestation ..)
• global dimming (aerosols in the atmosphere)
• change of amount and pattern of precipitation
• extreme weather conditions
• species extinctions
• changes in agricultural fields
• retreat of glaciers & sea ice
• sea-level rise
Temperature RiseCommon measure of global warming: the trend in globally averaged temperature near the Earth’s surface
1906-2005 0.74±0.18 C
Warming rate NOT constant!!
Since 1979:Land: 0.25 C per decadeOcean: 0.13 C per decade
Oceans • larger effective heat capacity• lose more heat by evaporation
Predictions for 21st Century:
Now- 2100 1.1 to 6.4 C rise
Current Sea-Level Rise
Mean Rate of Sea-Level Rise
Past century: 1.8 mm/year
Since the satellite sea-level measurements (1993-onwards): 2.8-3.1 mm/year
Increasing Temperatures:
• sea level rise by thermal expansion of water
• melting of mountain glaciers, ice caps & ice sheets
Sea-Level Rise & Glacier Retreat-High precision gravimetry from satellites - ground estimates
Greenland & Antarctica are losing millions of tons of ice per year
Sea-Level Rise Extremes:
• IF small glaciers & ice caps at the edges of Greenland & Antarctic ice sheets melt -> 0.5 m rise• IF Greenland ice sheet melt -> 7.2 m rise• IF Antarctic ice sheet melt -> 61 m rise
BUT the interiors of Greenland & Antarctic ice sheets cannot melt in less than several millennia -> melting of interiors will
not contribute in the 21st century
1973 Whitechuck Glacier 2006 Whitechuck glacier
Trift Glacier, Switzerland
1948 2006
Kilimanjaro glacier, Africa
1993
2000
Portage Glacier
Shepard Glacier
1913 2005
Sea-Level Back In Time…
120,000 years ago… Sea-Level 6 meters higher than today!
Evidence• wave-cut notches along cliffs in the Bahamas
• coral reefs 3 m above current sea-level along southwestern coastline of West Caicos island in West Indies -> must have stayed at that level long enough for reefs to grow
Parallel beds slightly dipping towards sea. West Caicos, West Indies.
18,000 years ago…(Ice Age)
Sea-Level 120 meters lower than today!
• thousands of cubic meters of ice stacked up on the continents as glaciers
• Dry connection between Asia and Alaska over which humans are believed to have migrated to North America!
Sea-Level Back In Time…
Sea-Level Rise Not Uniform Globally..Global average: 1.8 mm/year
BUT considerable variation:• some land areas sinking while others are rising
• 9.1 mm/year of sea-level rise along Louisiana coast due to land sinking
• drop of sea-level in parts of Alaska due to post-glacial rebound
• Sea-Level rise in Australia of 1mm/year
• rise of 1.5mm/year for Netherlands (measurements since 1850)
Sea level rise relative to the predicted global average for the years 2080-2099 minus the average for 1980-1999.
Rate of Sea-Level Rise Increasing?
2002
2005
500 billion tonne Larsen B ice shelf (twice the size of London) -> disintegrated in less than a month!
British Antarctic Survey: 87% of glaciers on Antarctic Peninsula have retreated over past 50 years
1979 Boundary
Future Sea-Level Rise Rise by 2100-> upper limit of 2 meters
-> most probable rise of 0.8 meters taking into consideration the rate at which ice can melt
Greenland
• local warming in Greenland will exceed 3 C in this century
• initiate long-term melting of ice sheet
Antarctica• West Antarctica (1992-onwards): 50 Gigatonnes of ice loss per year• East Antarctica: positive mass balance -> lowers/ balances sea-level
Future Sea-Level Rise
Impacts of Sea-Level Rise
• catastrophic for shore-based communities • serious impacts on agriculture : ¾ of the population in developing countries depend on agriculture systems
• coastal erosion
• contamination of fresh water by salt water
• extreme weather conditions & high frequency of flooding• species extinctions
• 634 million people live in low-lying coastal areas
• small island states vulnerable
Threatened Countries & Cities I
LondonNew Orleans
• need strorm surge defenses• also sinking land
Netherlands
• 25 % of the country is beneath sea-level
• massive new building program to strengthen the country’s water defenses for the next 190 years• 100 billion Euros to be spent through 2100 to broaden coastal dunes and to strengthen sea & river dikes• worst-case plans for evacuation
1 m below sea level
Threatened Countries & Cities II
Nigeria • Rise of just 200 mm could create 740,000 homeless people
Bangladesh• Rise of 400 mm in Bay of Bengal would result in 11 % of Bangladesh’s coastal land being underwater• 7-10 million climate refugees• reduce the country’s rice farmlands by 50 %
NY, Bangkok, Islands of Tuvalu
etc
• also at high risk..
8m sea level rise
Threatened Countries & Cities III
Maldives
• most population lives on land within 2 meters of sea-level
• capital Male : - fresh water only in the centre of the island -salt water penetration already resulted in loss of mango trees - series of breakwaters on its outer coast to protect island from tides
• other small islands of Maldives, e.g. Thulhaadhoo - most land 70 cm above water !! - some areas only 35 cm above water
uninhabitable by 2100 - > president proposed buying land in Thailand or Sri Lanka because of similar culture BUT buying land in Australia most probable due to the amount of unoccupied space in the country.
Solutions for Current & Future Sea-Level Rise
Current policies for limiting emission are not sufficient**even if emission were stabilized at present, a further warming of 0.5 C would still
occur – climate takes centuries to adjust to changes **
• Building dikes too expensive Costs of adapting to 1m rise in the US -> 156 billion!!
• use cleaner & less polluting technologies• use of renewable energy• carbon capture & storage ( trap CO2 produced by factories, gas or coal stations and store it e.g., underground)• GHGs stabilized at a level where ecosystems can adapt naturally, food production not threatened & economic development can proceed in a sustainable fashion• aim of UNFCCC (United Nations Framework Convention on Climate Change) countries -> limit future increase in global mean temperature below 2 C
BUT also start preparing for occurring sea-level rise • high risk countries to start building defenses • budget building programs in developing countries• start preparing for possible migration of population in low-lying cities