Transcript Recent Warming of Antarctic Bottom Water in the South Atlantic

7th Annual Summer Institute
and
Friday Harbor Laboratory Centennial Symposium
How Does Ocean Circulation Matter for Climate
Change?
Sept. 14-17, 2008
Friday Harbor Laboratories, San Juan Island, WA
The thermohaline circulation is sometimes called the ocean conveyor belt,
the great ocean conveyor, or the global conveyor belt. On occasion, it is
mistaken to mean the meridional overturning circulation (often abbreviated
as MOC), but is distinct from it in two ways. Firstly, the MOC only occurs
around the meridian - hence the name - and so is confined to the Atlantic
Ocean. Secondly, there is published data on the MOC's existence, whilst
the thermohaline circulation remains a purely theoretical conjecture.
Wickipedia (Updated September 2, 2008)
AABW and NADW Volumes (Johnson 2008)
•Volume integrate the fraction of
AABW at each location
NADW
•Logarithmic Scale
•NADW 21% of the global ocean
volume
AAB
W
•AABW 36% of the global ocean
volume
•AABW has at least 1.7 times
the volume of NADW
The Indian Ocean
Warming is apparent in the southern ocean
SE Indian Ocean
1994/5 & 2007
Johnson, Purkey, & Bullister (in press)
13-year time interval 2007- 1994/5
0.1C abyssal warming=0.9W/m2
4cm Sea level rise
Isolated to southern basins
The Pacific Ocean
MOC Active in Pacific, but shallow. Ocean
drives fluxes to the atmosphere in the
western boundary current
MOC and Salinity
Coupled model
Ocean Only
Model
Thompson
and Cheng
2008
Sea Surface Height Variability and
Mean Path of Kuroshio
10 km model
Altimeter
Observations
Upper Ocean Heat Budget
From a High Resolution Ocean Model
Heat storage rate = surface flux +
lateral flux + isotherm motion
Advection dominates (as in observationally derived
budget) (Kelly et al, 2007)
The Atlantic Ocean
Connection between the mid and
high latitudes is complex, and
linked to the atmosphere
No ice
Ice
Stream
Function
T
anomaly
Steve Yeager, NCAR
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Mike McCartney, WHOI
Winter 850mb Storm Track
Winter Surface Storm Track
Winter Stability of boundary layer
Booth et al, 2008
Influence of the Gulf Stream on the troposphere
Minobe et al, Nature, 2008 (picture from the New Scientist, March, 2008)
Questions from PCC
discussion, August 2008
• What is the definition of the MOC? THC? Can
we separate the THC and wind-driven circulation?
• How should models be used to investigate ocean
circulation and its impact on climate in the past
and in the future?
• How fast does the circulation adjust in the deep
ocean, and how fast do the deep tracers change?
• How well do we understand paleo-circulation?
Are there limits to our knowledge?
More Questions:
• What is the relative importance of tropical and mid-latitude
SST variability for mid-latitude climate?
• Are ocean heat transport anomalies compensated by
atmospheric heat transport anomalies?
• Can internal processes alone generate atmospheric
variability?
• What background state in the atmosphere favors influence
of mid-latitudes SST on the atmosphere?
• What part of the high latitudes is important to climate?
South of 40S? North of 60N? Is sea-ice the key?
Schedule
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Breakfast 7:45-8:15 Monday-Wednesday
Morning Session 8:45-12:30
Lunch 12:30-1
Afternoons Free
Dinner 6-6:30
Evening Session 7-10:30
• Monday Morning
The Ocean in the Climate System
• Monday Evening
Ocean Circulation in the Past
Panel Discussion--Can the Ocean Circulation Change Drastically as
Implied by Paleo Data?
• Tuesday Morning
Variability of Ocean Circulation, Interannual to Decadal
• Tuesday Evening
The Carbon cycle, and land/ice interactions: what is the role for the
oceans in future and past climate change?
Panel Discussion--What can we say confidently? What is a reasonable
best guess about the role of the ocean in future climate change?
• Wednesday Morning
Debate: What can models tell us about ocean circulation and climate?
Summary Presentation