Mass and Volume Contribution to Twentieth-century Global

Sea Level Rise

L. Miller & B. C. Douglas

Nature vol. 428, 2004

Could water world really happen?

Interaction of temperature change with environmental system

Water held in glaciers and small ice caps!!

Greenland Ice Sheet7m GSLR

Antarctic+ GLIS80m GSLR

But by how much ?

1. Volume Change (Total Steric Sea Level, TSSL)

2. Mass Change (Eustatic change)

Exchange of water with atmosphere and continents

Temperature and salinity variations

Gauge Data

Total Steric Changes +Eustatic Changes

Isostatic Changes

Dynamic Height

Depth difference between two surfaces of constant pressure and gravity.

It is derived from hydrographic data (T, S, P)Ocean General Circulation Models (OGCM)

Different Approaches

Yearly average trend 1993-98 (3.2 + 0.2 mm/yr)TSC (temperature) (0-500m) 1993-98 (3.1 + 0.4mm/yr)Residual sea level (0.2 + 0.2 mm/yr)

5 year data trend

Topex/ Poseidon data from 1993-2001 (Cabanes et al., 2001)

*Global mean TSC (0-3000m) (0.5 + 0.05 mm/yr)*Pseudo global mean TSC using data of 25 gauge sites (1.4 + 0.2 mm/yr)*PSMSL record at 25 tide gauge sites (1.6+0.15 mm/yr)

*TSSL= 0.55 + 0.07 mm/yr*HSC 0.05 + 0.02 mm/yr

*470 + 170 km3/yr fresh water*Mass increase 1.35+0.5 mm/yr

(Antonov et al., 2002)

3rd IPCC report (2001)

IPCC adopted best estimates = 1.5 + 0.5 mm/yr

TSC = 0.7 mm/yr

CG = 0.2-0.4 mm/yr

MC = -0.2-0.6 mm/yr

TWS = -1.1- 0.4 mm/yr Sum = -0.8 –2.2 mm/yrAvg = 0.7 mm/yr

0

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+

Comparison of hydrographic and tide gauge measured sea level change in the

Eastern Pacific

TSSL = 0.5 mm/yrGauge data = 2 mm/yr

Local comparison

a. 0.5 mm/yr

c. 0.9 mm/yrGauge data = 1.7 mm/yr

b. 0.3 mm/yr

Regional comparison in the Eastern N. Atlantic

TSSL = 0.2 mm/yr

Gauge data = 2.1 &

1.9 mm/yr

Regional comparison in the Western N. Atlantic

Gauge data =1.9 mm/yr

Cabanes etal., 20018 sites = 0.5 mm/yr1 site = 6.7 mm/yr (NA)Avg = 1.2 mm/yr

Conclusions

*Overall gauge data = 1.5- 2.0 mm/yr GSLR for 20th century

Hydrographic data = 0.5 mm/yr

Mass Increase due to freshening = 1.4 mm/yr

* Satellite data = 2.5 mm/yr (1993-2003) Decadal data !!

Ocean freshening, sea level rising, sea ice meltingP. Wadhams, W. Munk(GRL., Vol. 31, 2004)

Arctic Sea Ice melting = (625 + 125) Km3/yr

Antarctic Ice thickening = (90 + 3) Km3/yr

Volume of fresh water = (325 + 105) Km3/yr

GSLR = mass + volume 0.6 + 0.5 = 1.1 mm/yr

Thanks

Total steric sea level change

1.Thermosteric change (TC)

2. Halosteric change (SC)

Mass and Volume

L. Miller & B. C. Douglas

Nature vol. 428 2004