Atm s 111 global warming understanding the forecast
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ATM S 111, Global Warming: Understanding the Forecast. Dargan M. W. Frierson Department of Atmospheric Sciences Day 8: 04/ 22/ 2010. The Oceans ( RG p. 106-127 ). From sticks to satellites: measuring sea level Monitoring the ocean below the surface Balancing the sea level budget

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ATM S 111, Global Warming: Understanding the Forecast

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ATM S 111, Global Warming: Understanding the Forecast

Dargan M. W. Frierson

Department of Atmospheric Sciences

Day 8: 04/22/2010


The Oceans (RG p. 106-127)

From sticks to satellites: measuring sea level

Monitoring the ocean below the surface

Balancing the sea level budget

How high the sea?

Climate change and El Niño

Will the Atlantic turn cold on Britain

Living in a changing sea

Coral reefs at risk

ocean acidification


20th Century Sea Level Rise

20th century sea level rise was 12-22 mm/decade on average

red = “reconstructed” from tide

gauges and other sources

blue = tide gauges

black = satellite altimetry


Mean Sea Level - The average height of the ocean at a given location

What controls it?

Thermal expansion of the ocean

The exchange of seawater/ice with lake/soil water or land ice

Tides

Ocean currents

Atmospheric winds

Tsunamis

The first two vary with

global warming


From sticks to satellites: measuring sea level

Tide gauges are measuring sticks

or sometimes floats in wells

Always coastal

Few long records


From sticks to satellites: measuring sea level

TOPEX-Poseidon Radar Altimetry

Instruments emits a short radar flash and measures the time-of-flight of its reflection from earth. 1,000 times per second.

Measures sea level and ice

sheet height


Sea level rise from TOPEX-Poseidon Radar Altimetry

Each 10 day measurement has an accuracy of 3-4 mm


No more enigma

Balancing the Sea Level Rise Budget

  • IPCC 2007 Figure 5.21.

1961 to 2003 (blue)

1993 to 2003 (brown)

~60%

~25%

~15%


Monitoring the ocean

Many instruments are used

to measure ocean heat

content


Argo floats

StephenRiser,

UW Oceanography


Monitoring the ocean heat content

Argo floats, since ~2000 measure

to 2000m depth


Monitoring the ocean heat content

Expendable Bathyermographs (XBT)

About 70 Voluntary ships toss them overboard

14,000 each year (they are cheap, even these figures are ugly)

measure down to 1500 m, in use since 1962


Ocean Heat Content

Observations in black with uncertainty shaded grey

Models are colored lines - span the observations

1950 1960 1970 1980 1990 2000

Domingues et al 2008


What will sea level be by the end of the 21st century?

200-500 mm

for 3 intermediate

scenarios

But had no

increase in

dynamical

thinning from

Greenland and

Antarctica!

Criticized by

James Hansen

FAQ 5.1, Figure 1


More recent estimates:

0.5 to 1.4 m by considering past SLR to past warming dependence and used IPCC estimate of future warming, Rahmstorf 2007

http://www.sciencemag.org/cgi/content/abstract/315/5810/368

Accelerated but plausible dynamic thinning could give 0.8-2 m

Pfeffer et al 2008

http://www.sciencemag.org/cgi/content/abstract/321/5894/1340


The very latest on Greenland

from the GRACE superstar

GRACE - Gravity Recovery and Climate Experiments

Greenland contributed 0.5 mm/yr to SLR between 2000-2008

or 237 Gt/yr loss

more than 2X the IPCC 2007

estimate for 1993-2003

van den Broeke et al 2009

D=dynamic loss (+ = loss),

SMB = accumulation - ablation


The very latest on Antarctica from the GRACE superstar

2002-2009 Antarctica losing ice - despite increased snowfall

cause - dynamic thinning

http://grace.jpl.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=33

192 +/- 92 Gt/yr from 1996-2006 according to Rignot et al 2008


Frequency of storm surge passing a given

threshold is likely to be as serious as mean sea level rise


“The Day After Tomorrow” had it wrong: a disintegrating floating ice shelf

is sea level neutral. The cooling that ensued should have caused sea level to drop!


Gulf Stream

transports heat

it is mostly

wind driven

(not subject to

stopping)

North

America

Gulf Stream

Colors show

Temperature

AVHRR satellite


Thermohaline circulation driven by buoyancy

differences also moves heat


Atlantic circulation

Red branches carry

heat northward

When water loses enough

heat it tends to sink

Weaken this circulation

would cool England and

Norway

Global warming is

expected to weaken the

portion that is buoyancy

driven as the water

would not lose as much

heat.


Coral reefs at risk


Coral reefs at risk


Coral reefs at risk

Coral bleaching


Coral reefs at risk

Coral bleaching


Another risk to coral: ocean acidification


When CO2 dissolves in water, carbonic acid is produced via the reaction:

CO2 (aq) + H2O <-> H2CO3

This carbonic acid is like sparkling water.

Chemistry of ocean acidification

Coral reefs at risk

Coral bleaching

What happens when you open a can of sparkling water?

CO2 comes out of the water.

The opposite is happening on Earth today. So CO2 is going

into the ocean. And this acidifies the ocean…


Chemistry of ocean acidification

Coral reefs at risk

Coral bleaching

When CO2 dissolves in water, carbonic acid is produced via the reaction:

CO2 (aq) + H2O <-> H2CO3

Acid dissociate into ions, including hydrogen ion

H2CO3 <-> H++ HCO3-

The increase in the hydrogen ion concentration causes an increase in acidity, since acidity is defined by the pH scale, where pH = -log [H+] (so as hydrogen increases, the pH decreases).  This log scale means that for every unit decrease on the pH scale, the hydrogen ion concentration has increased 10-fold.

so far the hydrogen ion concentration has increased by 30%


Chemistry of ocean acidification

Coral reefs at risk

Coral bleaching

When CO2 dissolves in water, carbonic acid is produced via the reaction:

CO2 (aq) + H2O <-> H2CO3

Acid dissociate into ions, including hydrogen ion

H2CO3 <-> H++ HCO3-

H+ reacts with carbonate ion as in

H++ CO32-<-> HCO3-


In your stomach or in the ocean,

the chemistry is the same

Coral reefs at risk

Coral bleaching

The source of the carbonate ionsCO32-

is calcium carbonate CaCO3

Just as the Tums dissolve, creatures with shells dissolve…

such as phytoplankton, which are responsible for

1/3 of all photosynthesis on the planet and

feed the marine food web.


Coral reefs at risk

Ocean Acidification

Coral bleaching

pH

Pre-industrial (1700s) 8.18

Recent past (1990s) 8.10

2050 (2×CO2 = 560 ppm) 7.95

2100 (IS92a) 7.82


Harmful algal blooms (HABs)


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