AssignmentsAssignments Read Chapter 15: Short Term Climate Variability Read Chapter 15: Short Term Climate Variability (pp 289 (pp 289 –– 306; already talked about rest of chapter) 306; already talked about rest of chapter)  Read Chapter 13: 257 Read Chapter 13: 257 –– 267 (K267 (K--T Mass Extinction)T Mass Extinction) ProjectsProjectsStill missing 10 submissions???Still missing 10 submissions???Still missing 10 submissions???Still missing 10 submissions??? Generally good topics but almost all of them need to be better Generally good topics but almost all of them need to be better focused focused –– what can you actually get across in 5 to 7 minuteswhat can you actually get across in 5 to 7 minutes Some duplication Some duplication –– may be asking some of you to focus in may be asking some of you to focus in particular directionsparticular directions Corals and volcanoes particularly oversubscribed Corals and volcanoes particularly oversubscribed –– want to want to change?change? Papers Papers –– sent email to everyone who wants to write a sent email to everyone who wants to write a paper paper –– if you didn’t get it, see meif you didn’t get it, see meClimate ForcingsClimate Forcings Solar activity Faint early sun Snowball earthEarth-sun positionEarth-sun position Ice ages Aerosol Volcanism Asteroid impacts Greenhouse warmingGreenhouse warmingCorrection Correction –– Dome C vs. Dome C vs. VostokVostokElevation over 3000 m (9800 ft)Snow accumulation less than 2” per less than 2” per yearTerrain slope of 1/1000Dome C 4300 m (14,000 ft)Vostok, AntarcticaVostok, AntarcticaIce core Ice core sectionssectionsNational Ice Core Lab in Lakewood, ColoradoGreenland ice coresVostok core-- total depth = 3310 m-- estimated age = 420 kyCurves show independent estimates of depth-age relationshiprelationshipData available on web from NOAA Paleoclimate ProgramDome C ConcordiaDome C ConcordiaFrom Wikipedia –copyright protectedFrom Wikipedia –copyright protectedTemperature (degrees C) for May 10, 2009[-73 C = -100 F]Dome C (Concordia) Ice Core: 3260 m; ~810,000 yearsDeductionsDeductions Temperature change (Temperature change (1818O record) and O record) and CO2 concentration changes remarkably CO2 concentration changes remarkably consistent => even show same consistent => even show same asymmetryasymmetryCO2 appears to lag (follow behind) CO2 appears to lag (follow behind) CO2 appears to lag (follow behind) CO2 appears to lag (follow behind) temperature record by 500 to 1000 years temperature record by 500 to 1000 years ((not really visible on 100,000 time scalenot really visible on 100,000 time scale)) Likely Likely that there is some connection => that there is some connection => CO2 may play a role in the feedback CO2 may play a role in the feedback cyclecycleCO2 feedback loop?CO2 feedback loop?Oceans warm(Changes in orbital parameters?)Ocean releases CO2 to atmosphere (Warmer water releases CO2)CO2 increases greenhouse effectOcean warmsHow to store more CO2 in deep How to store more CO2 in deep oceanocean(released to atmosphere at timescale of 500 to (released to atmosphere at timescale of 500 to 1000 years)1000 years)1.1. Slow down deep ocean circulationSlow down deep ocean circulation Slow down return of enriched CO2 waterSlow down return of enriched CO2 waterIncrease photosynthesis in mixed layer (results in faster Increase photosynthesis in mixed layer (results in faster 2.2.Increase photosynthesis in mixed layer (results in faster Increase photosynthesis in mixed layer (results in faster pump)pump) Limited by nutrients (Fe, P, N)Limited by nutrients (Fe, P, N) Suggested ways to increase nutrientsSuggested ways to increase nutrients Exposed continental shelf sediments => erosion, weatheringExposed continental shelf sediments => erosion, weathering Arid climate => wind blown dust => FeArid climate => wind blown dust => Fe Growth and destruction of coral reefs => change CO2 amount in Growth and destruction of coral reefs => change CO2 amount in atmosphereatmosphereLessons learnedLessons learned Current climate is not the only possible one for Earth (indeed, glacial conditions seem to be preferred) A change in surface temperature of about -5C is associated with a massive climate shiftGlobal climate and CO2 appear to be intimately Global climate and CO2 appear to be intimately intertwined If the orbital parameter theory is right, small triggers can produce major climate changes under some conditions But… there are many remaining questions and enigmasEnd of glacial (~20,000 ybp)Beginning of Holecene(~12000 ybp)Greenland ice core300 yearsYounger Younger DryasDryas PeriodPeriod• Temperaturescome from Oand H isotopesin ice coresYounger Dryas• High 18O (or highD/H) ⇒ warmertemperaturesGlobal event Global event GISP2Cave in China (stalactite)The Atlantic Conveyor• Did the oceanic thermohaline circulation shut downduring the Younger Dryas Period?Extent of ice sheet ~15,000 ybpExtent of ice sheet ~15,000 ybpAtlantic Conveyor ShutdownAtlantic Conveyor Shutdown As the Laurentide ice sheet retreated, melt water was diverted from the Mississippi River to the St. Lawrence RiverAtlantic Conveyor ShutdownAtlantic Conveyor Shutdown As the Laurentide ice sheet retreated, melt water was diverted from the Mississippi River to the St. Lawrence RiverIce dam broke, releasing a huge amount of fresh Ice dam broke, releasing a huge amount of fresh water North Atlantic ocean became capped with freshwater ⇒ not dense enough to sink ⇒thermohaline circulation shut down for ~1000 yrs Could this happen again as a result of global warming?Solar variability and Holocene ClimateSolar variability and Holocene ClimateIrradiance based on sunspot variability (prior to 1970) Note scale: Change is 3 W/m2 out of 1364 W/m2 = 0.2%Can such small variability affect climate?Can such small variability affect climate? Variation is at high energy end of Variation is at high energy end of spectrum (UV) spectrum (UV) –– absorbed n the upper absorbed n the upper atmosphereatmosphereDefinitely correlations between Definitely correlations between Definitely correlations between Definitely correlations between temperature and sunspot activitytemperature and sunspot activityCan such