20 th century seaLevel change 1 The uncertain

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20 th century sea-Level change 1

20 th century sea-Level change 1

The uncertain sea level future The Earth’s ice is melting, sea level has increased

The uncertain sea level future The Earth’s ice is melting, sea level has increased ~3 inches since 1960 ~1 inch since 1993 -signs of accelerating melting are now clear -land ice particularly striking, poles more complicated -IPCC estimates project current trends forward i. e. LOWER estimate using no acceleration

Stroeve et al, 2008

Stroeve et al, 2008

Sea level rise: IPCC says 7” to 22” by 2100, much more if rapid

Sea level rise: IPCC says 7” to 22” by 2100, much more if rapid ice sheet collapse occurs most scientists would go on record for 1 m rise (30 inches)

During the last interglacial, temperatures were warmer than pre-industrial (by 5ºC), and sea level

During the last interglacial, temperatures were warmer than pre-industrial (by 5ºC), and sea level was higher by 5 -6 m Cuffey et al. , 2000 Greenland + West Antarctic = 14 m

Sea Level Change in the last 100 yr (from Tidal Gauges) Res. Curve =

Sea Level Change in the last 100 yr (from Tidal Gauges) Res. Curve = Obs. – Tides - Atmos. Press. = Observations of Sea Level Atmospheric Pressure + Tides 7

Measuring sea level changes in time: (in past times) 18 Differential incorporation of 18

Measuring sea level changes in time: (in past times) 18 Differential incorporation of 18 and 16 isotopes of oxygen into the calcium carbonate in the skeleton of marine organisms. (Read hand out!) Radio-carbon dating of continental margins (in modern times) tide gauges Located at coastal stations, they measure the relative change in sea level. altimetry Satellites in orbit around the planet use radar altimetry to measure the height of the sea level (accuracy of 2 cm). temperature of the ocean Thermal expansion of ocean changes in height (= Steric Sea Level) 8

WOCE Sea Level Stations as of February 2000 (from Tidal Gauges) WOCE is the

WOCE Sea Level Stations as of February 2000 (from Tidal Gauges) WOCE is the World Ocean Circulation Experiment http: //woce. nodc. noaa. gov/wdiu/ 9

What can we say about these tide gauges record? Arica Iquique Coquimbo 6/23/2001 6/24/2001

What can we say about these tide gauges record? Arica Iquique Coquimbo 6/23/2001 6/24/2001 10

Sea Level trend based on Tidal Gauges 11

Sea Level trend based on Tidal Gauges 11

altimetry Satellites in orbit around the planet use radar altimetry to measure the height

altimetry Satellites in orbit around the planet use radar altimetry to measure the height of the sea level (accuracy of 2 cm). http: //www. ecco-group. org/animations_iter 21/TP_ps 21. mpeg 12

Spatial pattern of sea level change 1993 -2003 (from Satellite) cm/yr 13

Spatial pattern of sea level change 1993 -2003 (from Satellite) cm/yr 13

Geographical distribution of sea level trends (in mm/yr) computed from TOPEX/POSEIDON altimetry between January

Geographical distribution of sea level trends (in mm/yr) computed from TOPEX/POSEIDON altimetry between January 1993 and December 1999. Yellow and red colors correspond to sea level rise, while blue color corresponds to sea level drop. 14

Sea Level Change in the last 10 yr (from Satellites) 15

Sea Level Change in the last 10 yr (from Satellites) 15

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An example of Temperature measurements: Expendable Bathythermograph (XBT) Lines XBT 17

An example of Temperature measurements: Expendable Bathythermograph (XBT) Lines XBT 17

Steric sea trend changes 1955 -1996 18

Steric sea trend changes 1955 -1996 18

Closer look at Sea Level Change in the last 100 yr from Tidal Gauges

Closer look at Sea Level Change in the last 100 yr from Tidal Gauges and Dynamic Height (=thermal expansion of oceans) Tidal Gauges Satellite 19

ol. 294. no. 5543, pp. 840 - 842 DOI: 10. 1126/science. 1063556 Reports Sea

ol. 294. no. 5543, pp. 840 - 842 DOI: 10. 1126/science. 1063556 Reports Sea Level Rise During Past 40 Years Determined from Satellite and in Situ Observations Cecile Cabanes, Anny Cazenave, Christian Le Provost The 3. 2 ± 0. 2 millimeter per year global mean sea level rise observed by the Topex/Poseidon satellite over 1993 -98 is fully explained by thermal expansion of the oceans. For the period 1955 -96, sea level rise derived from tide gauge data agrees well with thermal expansion computed at the same locations. However, we find that subsampling thermosteric sea level at usual tide gauge positions leads to a thermosteric sea level rise twice as large as the "true" global mean. As a possible consequence, the 20 th century sea level rise estimated from tide gauge records may have been overestimated. 20

Reconstruction of MSL using all data sources 21

Reconstruction of MSL using all data sources 21

The Earth's climate has warmed about 1°C (1. 8°F) during the last 100 years.

The Earth's climate has warmed about 1°C (1. 8°F) during the last 100 years. (the warming follows the Little Ice Age (19 th century) 1 -2 mm/yr sea level rise) thermal expansion of ocean water reduction in volume of ice caps, ice fields, and mountain glaciers IMPACTS of HUMAN on SEA LEVEL: Increase in greenhouse-gas emissions: Global Warming expansion of oceans many of the world's mountain glaciers will disappear sea level rise acceleration FUTURE: Numerical models of the Climate System can be used to predict future changes in Sea Level 22

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Other processes contributing to Mean Sea Level on shorter Timescales and on local spatial

Other processes contributing to Mean Sea Level on shorter Timescales and on local spatial scales. MSL 100 m 10 m Tsunami (Tidal waves) El NiÑo Ocean-Atmosphere interactions 1 m Vortices (Eddies) Wind generated waves Waves by ships Freshwater floods 1 cm Decadal changes in Ocean Circulation Planetary Waves Ocean Current Tides Atmospheric Pressure 1 min 1 hour 1 day TIME 30 days 1 year 10 yr 24

Spatial pattern of sea level change 1993 -2003 (from Satellite) Steric sea trend changes

Spatial pattern of sea level change 1993 -2003 (from Satellite) Steric sea trend changes 1955 -1996 (from ocean temperatures) 25

END of Lecture 26

END of Lecture 26

Review of Geomagnetic field What is the earth magnetic field and why is it

Review of Geomagnetic field What is the earth magnetic field and why is it important Explain the distribution of magnetic anomaly stripes, seismicity, and volcanism in terms of the concept of global plate tectonics. 27

What is a magnetic field? Magnetic fields are produced by electric currents, which can

What is a magnetic field? Magnetic fields are produced by electric currents, which can be macroscopic currents in wires, or microscopic currents associated with electrons in atomic orbits. The magnetic field B is defined in terms of force on moving charge in the Lorentz force law. Units Tesla=N s / (Coulomb m) = 10, 000 Gauss 28

magnetic bar solenoid 29

magnetic bar solenoid 29

Origin of the Magnetic Field Magnetic fields are produced by the motion of electrical

Origin of the Magnetic Field Magnetic fields are produced by the motion of electrical charges. For example, the magnetic field of a bar magnet results from the motion of negatively charged electrons in the magnet. The origin of the Earth's magnetic field is not completely understood, but is thought to be associated with electrical currents produced by the coupling of convective effects and rotation in the spinning liquid metallic outer core of iron and nickel. This mechanism is termed the dynamo effect. 30

Why do we care about the magnetic field? 31

Why do we care about the magnetic field? 31

Source of Solar Wind … 32

Source of Solar Wind … 32

The Earth's Magnetosphere 1) The solar wind is a stream of ionized gases that

The Earth's Magnetosphere 1) The solar wind is a stream of ionized gases that blows outward from the Sun at about 400 km/second. 2) The Earth's magnetic field shields it from much of the solar wind. When the solar wind encounters Earth's magnetic field it is deflected. 3) The magnetosphere represents a region of space dominated by the Earth's magnetic field in the sense that it largely prevents the solar wind from entering. 33

However, some high energy charged particles from the solar wind leak into the magnetosphere

However, some high energy charged particles from the solar wind leak into the magnetosphere and are the source of the charged particles trapped in the Van Allen belts. 34

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Geomagnetic Polarity Reversals 36

Geomagnetic Polarity Reversals 36

Magnetic Anomalies 37

Magnetic Anomalies 37

Example of Ocean Floor Magnetic Anomalies 38

Example of Ocean Floor Magnetic Anomalies 38

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End of lecture 40

End of lecture 40