Upload
others
View
5
Download
0
Embed Size (px)
Citation preview
Water - Its Properties and Role in the Environment
Outline:
• Role in early history and science
• Unique chemistry
• Hydrologic cycle - redistribution, climate effects
• Ocean circulation - basic wind & thermohaline
Chemically unique
Exists in all three phases at atmospheric temperatures & pressures
(high melting and boiling points compared to molecules of similar
size It is the only substance that does this!
• High heat capacity (4.2 J/g/K). It stores a lot of heat energy which
makes it a good medium for spreading the planet’s heat
• High heat of fusion (solid to liquid ~ 335 J/g/K) and vaporization
(liquid to gas ~ 2400 J/g/K) so more effectively transfers heat when
changing phase in atmosphere/ocean
Chemically and Physically unique
•Water is physically
unique because it is less
dense as a solid (ice) than
as a liquid.
•The maximum density of
liquid water occurs at 4ºC
Physically Unique
• High surface tension so it forms drops & helps make good cell
membranes
• Dissolve other compounds very easily and so can transport
chemicals (e.g., NaCl, nutrients)
• Mediates or facilitates most chemical reactions in living systems
(e.g., takes water to photosynthesize) - neutral pH
Chemically and
Biologically
Unique
Covalent and Ionic Bonds
Hydrogen Bonds - 10 x stronger than normal
intermolecular (van der Waals)
forces.
100%326,000,000Total water
volume
0.0001%300Rivers
0.001%3,100Atmosphere
0.005%16,000Soil moisture
0.008%25,000Inland seas
0.009%30,000Fresh-water lakes
0.61%2,000,000Ground water
2.14%7,000,000Icecaps, Glaciers
97.24%317,000,000Oceans
Percent of
total
water
Water volume, in
cubic milesWater source
Distribution of water
Hydrologic Cycle (in 103 km3)
Quantitative Hydrological Cycle
several hoursBiological water
8 daysAtmospheric moisture
16 daysChannel network
1 yearsSoil moisture
5 yearsBogs
17 yearsLakes
10000 yearsGround ice of the permafrost zone
1600 yearsMountain glaciers
9700 yearsPolar ice
1400 yearsGround water
2500 yearsWorld Ocean
Period of renewalWater of Hydrosphere
http://www.unesco.org/science/waterday2000/Cycle.htm
Period of Renewal
Aquifers
Freshwater Resources
1407000Flux
(cubic miles / year)
1400 yrs16 daysResidence Time
200000300Volume
(cubic miles)
GroundwaterRivers
Atmospheric circulation
Equatorial Hadley Cells
http://psb.usu.edu/psbdept/faculty/lh/bmet2000/Image56.gif
To see the animated version go to
http://geography.uoregon.edu/envchange/clim_animations/gifs/prate_web.gif
Precipitation
Rain shadow
Global warmingGlobal warming(temperature increase)(temperature increase)
Effects of global warming on water cycleEffects of global warming on water cycle
Speeds up globalSpeeds up globalwater cyclewater cycle
More extreme weather eventsMore extreme weather events
•• DroughtsDroughts
•• StormsStorms
•• FloodsFloods
Projected Changes in Annual Precipitation for the 2050sProjected Changes in Annual Precipitation for the 2050s
Source: The Met Office. Hadley Center for Climate Prediction and Research
The projected change is compared to the present day with a ~1% increase per year in equivalent COThe projected change is compared to the present day with a ~1% increase per year in equivalent CO22
GreenGreen •• = increasing, Brown= increasing, Brown •• = decreasing= decreasing
Global Precipitation TrendsGlobal Precipitation Trends
(% per decade) (% per decade) 1900 - 19941900 - 1994
Source: Watson 2001
U.S. Precipitation Trends: 1901 to 1998U.S. Precipitation Trends: 1901 to 1998
Source: National Climatic Data Center/NESDIS/NOAA
GreenGreen •• = increasing, Brown= increasing, Brown •• = decreasing= decreasing
All stations/trends displayed regardless of statistical significanceAll stations/trends displayed regardless of statistical significance
Extreme Precipitation Events in the U.S.Extreme Precipitation Events in the U.S.
Source: Karl, et.al. 1996.