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ENVIRONMENT:
Surface Temperature, Subsurface Temperature, and Wind Data
Surface Temperature is a measure
of the relative "hotness" or "coldness"
of the uppermost waters of the ocean.
This is different from measuring the
amount of heat that the oceans hold.
A candle may burn at a higher
temperature than a forest fire, but a
forest fire produces far more heat.
Similarly, the vastness and depth of
our oceans enable them to hold a
tremendous amount of heat, even
though temperatures vary from near
freezing to moderately warm. The two
Pacific Ocean study areas – "Coastal
California" and
"Tropical Pacific" – have different patterns of sea surface temperature,
mostly because of their positions relative to the equator. Situated greater than
35° north of the equator, sea surface temperatures in the "Coastal California"
study area are relatively cool – ranging from 10°C to 16°C (50°F to 61°F; see
color coded bar at left). On the other hand, "Tropical Pacific" ocean waters
are exposed to intense sunlight throughout the year. This leads to warm sea
surface temperatures – ranging from
19°C to 31°C (66°F to 88°F; see
color coded bar at right).
Subsurface Temperature is a measure of the relative
"hotness" or "coldness" of deeper waters of the ocean.
Whereas surface temperature data are displayed as maps,
subsurface data are displayed as "profiles" with shallower
waters at top and deeper waters at bottom. When analyzing
subsurface data, an important piece of information is its
location. For example, the easternmost extent of all "Coastal
California" profiles is Monterey Bay (as shown in the map at
left). The westernmost extent of this profile is about 300 km
(~180 mi) offshore. From the surface to 200 m (~650 ft)
depth, the range of subsurface temperatures in this area is
8°C to 16°C (46°F to 61°F; see color coded bar at right). For the
"Tropical Pacific" study area, subsurface data were taken along the
equator over 85° of longitude, an extent of 9,450 km (5,870 mi). From
the surface to about 500 m (1640 ft) depth, subsurface temperatures in
PHYTOPIA - UPWELLING ZONES - ENVIRONMENT OVERVIEW - PAGE 1
the "Tropical Pacific" study area range from
just above freezing to 32°C (90°F; see color
coded bar, at right).
Subsurface temperature data are important because they give clues about the types of
oceanographic processes occurring in a region. For example, cool temperatures through the
water column may indicate that nutrient-rich waters are moving vertically from depth to the
surface. Where this type of "upwelling" occurs, phytoplankton populations can grow
dramatically to fuel the marine food web. On the other hand, warm temperatures deep within the
water column may reveal unusual patterns of heat storage – for example, abnormal heat transfer
from the tropical Pacific Ocean to the overlying atmosphere that drives "El Niño weather."
Wind Data show the movement of air
near the sea surface. Winds can drive
ocean currents and mix ocean waters,
bringing colder, nutrient-rich waters to
the surface, aiding productivity. Wind
data are displayed as "vectors" – their
lengths show relative speed and
arrows indicate the wind direction. In
the "Coastal California" example at
right, all data vectors are shorter than
the reference arrow shown at far right
– thus all winds shown in this figure
are weaker than 10 meters per second (36 kilometers per hour or 22 miles per hour). The vectors'
directions indicate winds that predominantly blow out of the northwest, parallel to the coast.
Tropical wind patterns are dominated by "trade winds" – steady winds that blow from east-towest, located north and south
of the equator. As these
easterly winds converge,
moist air is forced upward.
This causes water vapor to
condense, or be "squeezed"
out, as the air cools and
rises, resulting in a band of
heavy precipitation around
the globe. This band of
clouds and rain – the
"Intertropical Convergence
Zone" – moves seasonally,
always drawn toward the
area of most intense solar
heating, or warmest ocean
temperatures.
PHYTOPIA - UPWELLING ZONES - ENVIRONMENT OVERVIEW - PAGE 2