Sack Lunch Seminars

SPECIAL DATE AND TIME: October 1st, 4:00pm Jennifer MACKINNON SCRIPPS Internal Waves across the Pacific and other turbulent stories

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October 10th: SPECIAL TIME/LOCATION: 11:00AM TO NOON IN ROOM 54-1510 Ian EISENMAN Harvard University Rain driven by ice sheets as a cause of past abrupt climate change

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The Younger Dryas cold period, which interrupted the transition from ice age to modern con- ditions in Greenland, is one of the most dramatic incidents of abrupt climate change reconstructed from paleoclimate proxy records. Here we suggest a mechanism by which the receding glacial ice sheets can cause the atmospheric circulation to enter a regime with greater net precipitation in the North Atlantic region. This leads to a significant reduction … Check the full abstract here

October 17th: Charles STOCK Princeton University Bottom-up and Top-down Forcing in a Simple Size-Structured Aquatic Ecosystem Model

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The effect of variations in bottom-up and top-down forcing upon the biomass spectrum (i.e., the distribution of biomass when organisms are grouped by size) is analyzed using a size-structured aquatic ecosystem model. The biomass spectrum is closely linked to the flow of energy from primary producers to fish. The parameters and mechanisms controlling steady-state model results are first diagnosed. It is shown that model solutions … Check the full abstract here

October 24th: Bror JONSSON Boston University Variability in the Continental Shelf Biological Pump revealed by Lagrangian Tracking of Satellite Chlorophyll

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Estimating the net rate at which the marine ecosystem converts carbon into phytoplankton biomass, and its variability amongst regions and over time, is crucial for our understanding the carbon cycle. Satellite chlorophyll or backscatter products give a synoptic picture of phytoplankton carbon (PC), but estimating production rates is difficult because the temporal change of PC results from the net community production (NCP) of PC, as well as from advection of the PC with the circulation. Here, we track the motion of satellite derived PC with a model ocean circulation velocities… Check the full abstract here

October 31st: Keith RODGERS Princeton Decadal variations in equatorial Pacific ecosystems and ferrocline/pycnocline decoupling

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he equatorial Pacific Ocean is known for its large interannual to decadal variability in circulation. In particular, the changes that occurred in 1976/77 have received considerable attention in the climate dynamics literature, and recently there has been much attention focused on changes that may have occurred there in 1997/98. Unfortunately, due to data sparsity, the impact of these changes or shifts on ocean biogeochemistry and ecosystems remains largely unknown. Here, a three dimensional ocean circulation model … Check the full abstract here