Download Major Ocean Currents

Major Ocean Currents
(continue…)
Indian Ocean
Polar Regions
(Southern Ocean; Arctic Ocean)
Indian Ocean
Unique in its
topography and forcing
(compared with the
Atlantic & Pacific)
WINDS
Persian Gulf
Arabian
Sea
Bay of
Bengal
Indian Ocean
Strong seasonal
wind pattern:
summer monsoon
Precipitation
Winter is the “dry” season
H
Summer Monsoon brings one of the
largest rainfall amounts in the world:
causing flooding in India & Bangladesh
L
Indian Ocean Currents:
•
little northern Indian
Ocean
• subjected to very
strong winds that
reverse seasonally so it
has a western boundary
current that also
reverses seasonally and
is strongest during the
SW monsoon.
NE MONSOON (Winter)
SW MONSOON (Summer)
Note: Southern Indian Ocean is more
“normal” – no significant seasonal
change, there is always a SEC, though
it gets pushed south in some seasons
by an ECC which in this ocean is S of
the equator rather than N.
The Agulhas Current (western boundary current) extends beyond the tip of
Africa and shed large eddies into the Atlantic Ocean
Simulation of eddies shed from the Agulhas Current
from the Fine Resolution Antarctic Model (FRAM; Webb
et al. UK)
Indonesian Throughflow:
• Important role in the connection between the Pacific & Indian Oceans
(input of warm-fresh Pacific waters to Indian Ocean)
• Driven by higher sea level in the Pacific and lower in the Indian Ocean
• Very complex- many islands and passages
• Important for climate change (global ocean conveyer belt)
Ocean Currents in Polar regions
• Arctic and Antarctic regions are very different:
– Arctic: a shallow sea connected to sub-arctic seas
through narrow passages
(is it a real ocean or a semi-enclosed sea?)
– Antarctic: a continent surrounded by deep continuous
current that connects all oceans
• Both are important sources for deep water mass
formation (more on this later…)
Antarctic Circumpolar Current (ACC)
• zonally continuous
around the globe
• transports waters
between oceans
• strongly forced yearround by westerly
winds
• strong currents
concentrated at Polar
and Subantarctic fronts
• large mean
(barotropic) transport
(~150Sv) and large
variability (seasonal,
eddy)
•unique momentum
balance between windstress and bottom drag
of ridges
Drake
Passage
(Tonzak et al (2003)
Drake Passage flow:
• barotropic
• large variability
• influenced by topography
ICE AROUND ANTARCTICA
February
Weddell
Sea
Ross
Sea
September
Eddies in the Antarctic Circumpolar Currents from
numerical ocean models (Geophysical Fluid
Dynamics Laboratory, Princeton)
Arctic Ocean
Circulation:
• wind-driving is small
(ice cover), tides are
weak. Circulation
seems driven mostly by
an eddy/topography
interaction (shallow sea
divided into sub
basins).
• The surface flow is
driven by inflows from
the Pacific (Bering
Strait, 85km x 45m) and
Atlantic (Fram Strait,
450km x 3000m).
ARCTIC OCEAN SURFACE CIRCULATION:
Input/output straits  Transport drift
Atlantic Ocean
Pacific Ocean
ICE COVER IN THE ARCTIC AND ANTARCTICA
The shrinking Arctic ice
median
ice edge
Average Ice Coverage
1979-1981
2003-2005
Antarctica:
Another potential
consequence of climate
change- icebergs breaking
from the shelf
Satellite monitoring
of icebergs
Impact of climate
change on ecosystem:
Examples: Polar Bears
in the Arctic and
Penguins in Antarctica
Reminders:
Wednesday Oct-30: no class
Monday Nov-4: review
Wednesday Nov-6: Exam#2
Last part of the course:
- Thermohaline circulation
- Waves and Tides
- The coastal ocean