1

Presented by:- Ulagadde R.P.

Dept.Of Applied Geology (M.sc.Part-Ii] School Of Earth Science Solapur University, Solapur

Seminar onSea level processes &

changes

2

3

4

Learning Objectives 

The shape of the planet: difference between Geoids and Ellipsoid

The concept of Mean Sea Level

Processes that control the Mean Sea Level and its changes

Sea level changes over millions of year

Measuring sea level (tide gauges, altimetry, 18)

Sea level rise in the last century and global warming

Economic implications of Sea level changes

5

Gravitational field effects on sea level

Sea Level VariationAstronomical Tidal Forces

Earth’s water closest to the moon is acted on more strongly by the moon’s gravity

The solid Earth is pulled harder than the water on the side opposite the moon

The Sun produces similar tidal forces and accounts for about 1/3 of ocean tides

7

What does it mean to be at an altitude of 4000 m?

It mean that I am 4000 m above the Mean Sea Level (MSL)

Causes of Sea Level Change

Terrestrial water storage,Terrestrial water storage,Extraction of groundwater,Extraction of groundwater,

Building reservoirsBuilding reservoirs Subsidence in river delta,Subsidence in river delta,Land movements,Land movements,

Tectonic displacementsTectonic displacements

Seepage into aquifersSeepage into aquifersCirculation changes,Circulation changes,

Storm surges,Storm surges,Water expands as it warmsWater expands as it warms

Exchange of ocean waterExchange of ocean waterwithwith

glaciers and ice sheetsglaciers and ice sheets

9

10

by definition:Mean Sea Level = 0 m = equilibrium level

Changes in volume of water Changes in shape and volume of ocean basins

Changes are measured as relative changes to a reference datum

This reference datum can be a fixed one (e.g. distance from the center of the earth) or local (coastline).

11

A change in volume of seawater in one ocean will affect the level in all others. Any such world-wide change in sea-level is called EUSTATIC SEA-LEVEL change

12

13

14

15

Sea Level Change

16

Other effects of plate tectonicse.g. Upper Cretaceous (90 Ma) MSL > 300 m

17

Summary of spatial-temporal scale of processes contributing to Mean Sea Level

TIME (years)

M

SL (

met

ers)

100 1000 100 Ka 10 Ma 100 Ma

1 cm

1 m

10 m

100 m

1 day

(A) Exchange of water with continents (Groundwater, Lakes, etc.)(B) Temperature expansion

(D) Plate Tectonics(C) Melting of ICE

• Thickness and area of continental crust• Thermal state of crust• Load on oceanic by land mass and sediments (can generate localized changes in MSL, e.g. subsidence of North Sea )

A,B,C change in volume of waterD change in shape of container

NOTE:

18

Sea Level Change in the last 100 yr (from Tidal Gauges)

Tides

AtmosphericPressure

+

=

Observationsof Sea Level

Res. Curve = Obs. – Tides - Atmos. Press.

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

20

Arica

Iquique

Coquimbo

6/23/2001 6/24/2001

What can we say about these tide gauges record?

21

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

Increase in greenhouse-gas emissions: Global Warming expansion of oceans many of the world's mountain glaciers will disappear sea level rise acceleration

IMPACTS of HUMAN on SEA LEVEL:

Numerical models of the Climate Systemcan be used to predict future changes in Sea Level

FUTURE:

22

23

Thank You……