Changes in the deep ocean conveyor and eolian eolian sediment sediment Changes in the deep ocean conveyor and transport caused by meltwater meltwater events in high latitudes events in high latitudes transport caused by Bernd J. Haupt Haupt & Dan & Dan Seidov Seidov Bernd J. http://www.essc.psu.edu/~bjhaupt http://www.essc.psu.edu/~bjhaupt http://www.essc.psu.edu/~dseidov http://www.essc.psu.edu/~dseidov
Global Ocean Conveyor Global Ocean Conveyor • Present-day ocean thermohaline circulation is driven by the deepwater sources in the Northern and Southern Hemisphere. • During the geologic past and in the foreseeable future the During the geologic past and in the foreseeable future the • balance of the sources can change, causing climate to differ balance of the sources can change, causing climate to differ dramatically from its present- dramatically from its present -day state. day state. Glacial Earth Glacial Earth
Stommel- -Arons Arons Ocean circulation (1958) Ocean circulation (1958) Stommel • Me Meridional ridional ocean circulation ocean circulation • is is responsible for responsible for poleward poleward heat transport. heat transport. • Present Present- -day ocean day ocean • circulation is driven by circulation is driven by deep- -water sources in high water sources in high deep latitudes. latitudes. • Geological past shows Geological past shows • substantial differences in substantial differences in ocean circulation during ocean circulation during NADW warm and cold climates. warm and cold climates. • Geological past shows that Geological past shows that • an imbalance between high an imbalance between high latitudinal deep- -water water latitudinal deep sources dramatically altered sources dramatically altered the climate. the climate AABW
Global Ocean (Salinity) Conveyor Belt Global Ocean (Salinity) Conveyor Belt The concept of the global conveyor was put forward by The concept of the global conveyor was put forward by W. Broecker Broecker in 1991 and has proved to be one of the most in 1991 and has proved to be one of the most W. fruitful ideas in paleoceanography paleoceanography. . fruitful ideas in
Structure of presentation Structure of presentation • Problems/questions Problems/questions • • What is the key to the large What is the key to the large- -scale ocean circulation? scale ocean circulation? • • What are the differences between southern and northern What are the differences between southern and northern • meltwater events? events? meltwater • Is a sea level rise possible without the meltdown of ice Is a sea level rise possible without the meltdown of ice • shields? shields? • What are the requirements for climate studies? What are the requirements for climate studies? • st set) 1 st • Experiments Experiments ( (1 set) and validation (past and present) and validation (past and present) • • How does one test a model? How does one test a model? • nd set) (past, present, and future) 2 nd • Experiments ( Experiments (2 set) (past, present, and future) • • What influences our climate pacemaker? ( What influences our climate pacemaker? (meltwater meltwater events events • and feedbacks) and feedbacks) • Conclusions Conclusions •
Structure of presentation Structure of presentation • Problems/questions Problems/questions • • Where is the key to the large Where is the key to the large- -scale ocean circulation? scale ocean circulation? • • What are the differences between southern and northern What are the differences between southern and northern • meltwater events? events? meltwater • Is a sea level rise possible without the meltdown of ice Is a sea level rise possible without the meltdown of ice • shields? shields? • Will Washington/Cancun be flooded? Will Washington/Cancun be flooded? • • What are the requirements for climate studies? What are the requirements for climate studies? • st set) and validation (past and present) 1 st • Experiments ( Experiments (1 set) and validation (past and present) • • How does one test a model? How does one test a model? • nd set) (past, present, and future) 2 nd • Experiments ( Experiments (2 set) (past, present, and future) • • What influences our climate pacemaker? ( What influences our climate pacemaker? (meltwater meltwater events events • and feedbacks) and feedbacks) • Conclusions Conclusions •
Requirements for climate studies Data Data CTD (conductivity, CTD (conductivity, • Observation Observation • temperature, temperature, • Remote sensing (satellite, airplanes) • Remote sensing (satellite, airplanes) and depth) and depth) • Measurements from vessels and Measurements from vessels and • helicopters helicopters • Platforms and moorings Platforms and moorings • • Sediment drillings at land and on sea • Sediment drillings at land and on sea Device from deep sea mooring Device from deep sea mooring Box corer and sediment sample Box corer and sediment sample
st set) and validation 1 st Experiment (1 set) and validation Experiment ( (past and present) ) (past and present How does one test a model? 1 st st possibility: possibility: Predict future, including waiting to see whether 1 Predict future, including waiting to see whether forecast is proven to be true forecast is proven to be true 2 nd nd possibility: possibility: Start model in the past and examine whether model Start model in the past and examine whether model 2 “predicts predicts” ” known facts (WITHOUT cheating!) known facts (WITHOUT cheating!) “ after R. Alley [2000] after R. Alley [2000] For all those who question computer models: For example, computer models are used to r models are used to For all those who question computer models: For example, compute develop cars, airplanes, houses, and bridges, and for some time have been used have been used to create to create develop cars, airplanes, houses, and bridges, and for some time � Correctly used models are as great help bombs and medicine. � bombs and medicine. Correctly used models are as great help in our daily life. in our daily life.
Global ocean circulation model Global ocean circulation model • MOM 2 (Modular ocean model version 2.2) from GFDL MOM 2 (Modular ocean model version 2.2) from GFDL • (Geophysical Fluid Dynamics Laboratory) (Geophysical Fluid Dynamics Laboratory) • Grid resolution: Grid resolution: - - horizontal: 6 x 4 horizontal: 6 x 4° ° (62 x 45 grid points) (62 x 45 grid points) • - vertical: 12 unevenly spaced layers vertical: 12 unevenly spaced layers - Bottom topography (ETOPO 5) Bottom topography (ETOPO 5)
Global ocean circulation model Global ocean circulation model The numerical model MOM 2 (Modular ocean model version 2.2) (Modular ocean model version 2.2) developed developed The numerical model MOM 2 at GFDL (Geophysical Fluid Dynamics Laboratory) has been used at Penn Penn at GFDL (Geophysical Fluid Dynamics Laboratory) has been used at State to address past and possible future changes in the ocean global State to address past and possible future changes in the ocean global conveyor. The model equations are solved with different boundary conditions conditions conveyor. The model equations are solved with different boundary representing glacial, interglacial, and possible global warming scenarios. scenarios. representing glacial, interglacial, and possible global warming Grid resolution: Grid resolution: Bottom topography (ETOPO 5) (ETOPO 5) Bottom topography • horizontal: 6 x 4 • horizontal: 6 x 4° ° (62 x 45 grid points) (62 x 45 grid points) • vertical: 12 unevenly spaced layers vertical: 12 unevenly spaced layers •
st set) 1 st Experiment (1 set) and validation and validation Experiment ( (past and present) (past and present) Exp. SST SSS PD Levitus and Boyer [1994] Levitus et al. [1994] CLIMAP [1981] is used everywhere The present-day SSS was globally MWE except for the North Atlantic to the north increased by 1 psu according to of 50°N and east of 40°W, where the Duplessy et al. [1991] (lower sea level); data from Weinelt [1993], summarized in the North Atlantic, to the north of by Sarnthein et al. [1995] and processed 10°N, the data set is from Duplessy et al. by Seidov et al. [1996], replace the [1991] and Weinelt [1993], and for the CLIMAP data. North Atlantic to the north of 50°N and east of 40°W, where the data from Weinelt [1993] are used. All data were summarized by Sarnthein et al. [1995] and processed by Seidov et al. [1996] • SST SST = sea surface temperature = sea surface temperature • PD PD = present- -day day • • = present • SSS SSS = sea surface salinity = sea surface salinity • MWE MWE = meltwater event = meltwater event • •
Sea surface boundary conditions Sea surface boundary conditions Control experiment Control experiment Northern meltwater experiment Northern meltwater experiment T T PD MWE e e m m p p e e r r a a t t u u r r e e PD MWE S S a a l l i i n n i i t t y y
Water mass transport in Sverdrup Sverdrup Water mass transport in Vertical integrated transport above 1500 m Vertical integrated transport above 1500 m PD MWE Vertical integrated transport below 1500 m Vertical integrated transport below 1500 m MWE PD ? ? 6 m 1 Sverdrup (Sv) = 10 6 m 3 3 s s - -1 1 1 Sverdrup (Sv) = 10
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