oceanography

Oceanography

http://antwrp.gsfc.nasa.gov/apod/image/earth_1_apollo17_big.gif

The Oceans

Ocean Facts: Covers 71% of the earth’s surface Accounts for 97% of the water on earth

(rest in land ice, groundwater, lakes & rivers)

Average depth ~ 4,000 meters Average temp ~ 4oC (only 39oF) Average salinity ~ 35‰ = 3.5%

(1 meter = 3.3 feet)

The Oceans

Ocean Zones

Horizontal divisions: Coastal (neritic) = on/over shelf (shallow) Oceanic = beyond continental shelf (deep)

benthicshelf

oceaniccoastal

benthicabyss

Ocean Zones

Vertical divisions: Pelagic = open

water Epipelagic

(0-200m) Mesopelagic

(200-1000m) Bathypelagic+

(1000m+) Benthic = ocean bottom

benthicshelf

oceaniccoastal

benthicabyss

Continental Margins

Continental shelf As narrow as <1 km (0.6 mi) at active

margins (tectonic activity) As wide as >750 km (470 mi) at passive

margins (in middle of plates) Shallow, typically <200 m (600 ft) Only 8% of ocean surface, but biologically

richest part of ocean

Continental Shelf Intertidal zone (between high and low tides) – open, exposed

Sandy shores (Atlantic – Cape Cod and south) Rocky shores (most Pacific, Atlantic – north of Cape Cod)

Continental Shelf Intertidal zone (between high and low tides) – protected, muddy

Salt marshes (temperate) Mangrove forests (tropical)

Tides are affected by both the moon and the sun Tidal day = 24 hours, 50 minutes

Tides

Tides

Continental Shelf Estuaries - any semi-enclosed coastal area where freshwater and seawater meet and mix

Long Island Sound

http://www.epa.gov/region01/eco/lis/facts.html

http://www.estuary.cog.ny.us/index.html

South Shore Bays

http://www.epa.gov/owow/estuaries/programs/studies/pb.gif

http://www.peconicestuary.org/CCMP_PDF/Chpt4.habitat.pdf

Peconic Bay

Continental Shelf Subtidal zone (always underwater)

Soft-bottom (sand, mud) Unvegetated Seagrass beds

NOAA

Continental Shelf Subtidal zone (always underwater)

Hard-bottom Seaweed, kelp forests Coral reefs

Continental Margins

http://oceanexplorer.noaa.gov/explorations/02hudson/background/mapping/mapping.html http://soundwaves.usgs.gov/2005/01/research.html

Deep-Ocean BasinsDeep sea floor features: Averages ~4000m (13,000 ft, 2.5 mi)

http://oceanworld.tamu.edu/resources/ocng_textbook/chapter03/Images/Fig3-6.jpg

Deep Ocean Bottom Soft bottom (most common):

Abyssal plains Silt, clay, biogenic oozes (forams, diatoms, radiolarians)

http://www.deepseascape.org/index.phphttp://earthobservatory.nasa.gov/Study/Paleoclimatology_SedimentCores/Images/ocean_detritus.jpg

Hard bottom: Seamounts Ridges Deep coral reefs

NOAA

http://www.savethehighseas.org/photo_gallery.cfm?Cat=1

Deep Ocean Bottom

Hydrothermal Vents

Hydrothermal Vents

http://www.dfo-mpo.gc.ca/communic/endeavour/photo_e.htm

High temperature High chemical concentrations High acidity

Chemosynthesis – energy from chemicals, not the sun

Chemosynthetic bacteria, archaea:

Outside on rocks Inside some animals (tube worms, mussels, clams)

An oasis of warmth and food for other animals

Hydrothermal Vents

http://www.teara.govt.nz/NR/rdonlyres/E84896E2-2F7E-4D2A-9D46-366B50558303/87497/p5365dop.jpg http://oregonstate.edu/dept/ncs/photos/grazers.jpg

Brine pools: Gulf of Mexico was shallow sea that dried up in Jurassic period Thick layer of salts covered with sediment when seawater returned Salt seeps up through cracks in sediment

NOAA

Cold Seeps

Brine pools: Underwater lakes of super salty water Methane gases also seep out

NOAA

depth 700 m

Cold Seeps

Cold Seeps

NOAA

Chemosynthetic bacteria in mussels An oasis of food

http://dx.doi.org/10.1371/journal.pbio.0030102

Water

Water is unique and critical for life Viscous, thick medium Slow to heat up & cool down, regulates climate Exists in 3 states on earth Maximum density at 4°C, not 0°C (ice floats, insulates) Universal solvent

Seawater

Seawater is a complex solution of dissolved ions and other dissolved solids and gasses

Salinity Salinity = the total amount of dissolved salts in water Average amount = 35 g salt/1000 g seawater = 3.5%

= 35‰ (parts per thousand) Can be 0‰ at river mouths and >40‰ in parts of Red

Sea

Salts in Seawater

major

minor

Temperature

Califo

rnia C

urren

t

Gul

f Str

eam

SargassoSea

The density of water is a function of its temperature and salinity Density increases with lower temperature (until 4°C)

Density

http://upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Density_of_ice_and_water_%28en%29.svg/573px-Density_of_ice_and_water_%28en%29.svg.png

← Cold water (max. 1000 at 4°C)

← Warm water (958 at 100°C)

← Solid ice (917 at 0°C)

← Water vapor (1.2)

The density of water is a function of its temperature and salinity Density increases with higher salinity Cold salty water is the densest of all

Density

http://www.marietta.edu/~biol/biomes/physsal.gif

← Salty water (1027)

← Fresh water (1000)

3 stratified layers according to density: Surface mixed layer (epipelagic)

Mixed by wind and waves Warmer and less dense Up to 200m deep

Intermediate transition layer (mesopelagic) Deep stable layer (bathypelagic & beyond)

Colder and denser Below 1000m

Density, Temperature, and Salinity

Density, Temperature, and Salinity

pycnocline

halocline

200 -

Density, Temperature, and Salinity

Dissolved Gasses Most gases easily dissolve in seawater, but ocean proportions differ greatly from atmospheric proportions Carbon dioxide is very soluble (0.039% of atmosphere, 15% of gases in ocean) Oxygen is not very soluble (much less than in atmosphere) Unlike solids, gases dissolve better in cold water, so all gas concentrations are higher in the polar waters than the tropics

Dissolved Gasses

Oxygen minimum zone -

decomposition of organic matter

Highest at surface –mixing with air

High at bottom –deep water formed at surface

Dissolved Gasses

http://longislandsoundstudy.net/wp-content/uploads/2010/08/Hypoxia.jpghttp://www.gulfhypoxia.net/overview/images/image005.png

Hypoxia = low oxygen (<3 mg/l) Anoxia = no oxygen Stressful or deadly for marine life

Dissolved Gasses

Hypoxia in Long Island Sound every summer

http://longislandsoundstudy.net/wp-content/uploads/2010/07/freq-of-hypoxia-2011.jpg

Dissolved Gasses

http://theotherco2problem.files.wordpress.com/2009/11/ocean-chemistry.gif

Increased CO2 in air → more in the ocean Increase in H+ ions makes water more acidic,

pH 8.2→8.1, expected 7.6-7.8 by 2100

Dissolved Gasses

http://www.ucar.edu/communications/Final_acidification.pdf

“Ocean acidification” Bad for organisms with calcium carbonate shells

http://s.ngm.com/2007/11/marine-micro/img/ftr-hdr-acid.jpg

Dissolved Gasses

http://3.bp.blogspot.com/-9MpFK0zekqo/T-s8Mzm9qjI/AAAAAAAAB-c/5zsexadUp8A/s1600/oceanacidification.jpg

Light in the Ocean

Most sunlight does not penetrate very far into the ocean

transparency depends upon suspended matter deeper in tropics, less in coastal

Blocked by scattering and absorption Different colors penetrate to different depths

NOAA

Light in the Ocean

Light in the OceanEpipelagic = photic zone(bright light, all plants/algae)

Mesopelagic = twilight zone(little light, no plants/algae)

Bathypelagic = aphotic zone (no light, no plants/algae)

Pressure in the Ocean

Water is heavier than air Pressure increases with increasing water depth Sea level = 1 atm. of pressure In ocean, each 10m of depth (33ft) you add another atm. of pressure

Pressure in the Ocean

http://www.naturalsciences.org/education/deepsea/images/cups_before_after.jpg

Before and after travelling to 2000 ft