1. 20th century sea-Level change

2. 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

4. Stroeve et al, 2008

5. 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 1m rise (30 inches)

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

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

8. 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)

9. WOCE Sea Level Stations as of February 2000 (from Tidal Gauges)
WOCE is the World Ocean Circulation Experiment 

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

11. Sea Level trend based on Tidal Gauges

12. altimetry
Satellites in orbit around the planet use radar altimetry to measure the height of the sea level (accuracy of 2 cm).

13. Spatial pattern of sea level change
(from Satellite)
cm/yr

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

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

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

18. Steric sea trend changes 1955-1996

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

20. ol no. 5543, pp
DOI: /science
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 is fully explained by thermal expansion of the oceans. For the period , sea level rise derived from tide gauge data agrees well with thermal expansion computed at the same locations. However, we find that subsampling the 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 20th century sea level rise estimated from tide gauge records may have been overestimated.

21. Reconstruction of MSL using all data sources

22. The Earth's climate has warmed about 1°C (1
The Earth's climate has warmed about 1°C (1.8°F) during the last 100 years.
(the warming follows the Little Ice Age (19th century)  1-2 mm/yr sea level rise)
reduction in volume of ice caps, ice fields, and mountain glaciers
thermal expansion of ocean water
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

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

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

26. END of Lecture

27. 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.

28. 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

29. magnetic bar
solenoid

30. 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.

31. Why do we care about the magnetic field?

32. Source of Solar Wind …

33. 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.

34. 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.

36. Geomagnetic Polarity Reversals

37. Magnetic Anomalies

38. Example of Ocean Floor
Magnetic Anomalies

40. End of lecture