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