The Greenhouse Effect, the Oceans and Climate Change
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Greenhouse The glass used for a greenhouse works as a selective transmission medium for different spectral frequencies, and its effect is to trap energy within the greenhouse, which heats both the plants and the ground inside it. Greenhouses thus work by utilizing electromagnetic radiation and preventing convection.
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Greenhouse Effect
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
1
Earth’s Atmospheric Greenhouse
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Greenhouse Gases
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Analysis of CO2 • Non-dispersive infrared CO2 detector – Uses IR light, shone through an optical cell and detected on the other side of the gas sample, to quantify CO2 concentration. – It is an established and useful fact that CO2 absorbs IR radiation.
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
2
Greenhouse Gas Variability • Sources: – Volcanoes • CO2, NOx
– Biomass burning • CO2 from forest fires, natural and otherwise
– Bacteria • CH4 in ocean sediments (perhaps thermogenic)
– Fossil fuel burning • CO2, Anthropogenic EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Greenhouse Gas Variability • In deep past (Phanerozoic), CO2 concentration is very difficult to determine • Most evidence points to relationship with volcanic cycles
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Greenhouse Gas Variability
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
3
Greenhouse Gas Variability • Ice core record provides much more direct CO2 measurement • 420,000 y of ice core records of ice age cycles, related to CO2 concentrations
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Glacial – Interglacial CO2 Variability • Temperature and CO2 concentration are intimately related • Sometimes temperature leads CO2 and vice versa. – Feedback http://sitemaker.umich.edu/section2_group1/arctic_issues__permafrost
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Milankovitch Cycles • Milankovitch, a Serb physicist, had proposed orbital cycles • 3 cycles – 100,000 y – 41,000 y – 19,000 and 23,000 y
• Published 1930, ignored
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/climate.htm
4
Insolation Variability of Eccentricity • Insolation effects yield an incongruous response • What was the cause?
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
The Thermohaline Circulation • • • •
Cooling of salty GSS waters Formation of NADW Cross-equatorial transport Amplifier of orbital changes
http://www.onr.navy.mil/Focus/ocean/motion/currents1.htm
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography http://www.pik-potsdam.de/~stefan/thc_fact_sheet.html
Nonlinear-climate system • Multiple factors to climate change – Albedo • Ice cover • Exposed continental shelf • Sea ice
– Water vapor availability – Fresh water discharge into N. Atlantic
• All have feedbacks that can amplify orbital insolation changes EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
5
Ocean Heat Content • Heat content of the oceans: – – – – – –
• Heat content of atmosphere:
Specific heat: 1cal·g-1·oC-1 Volume: 1.37 x 109 km3 Density: 1.028 g·mL-1 Mass: 1.41 x 1024 g 5.9 x 1024 cal (to inc. 1K) 3.9 x 1026 cal (total)
EENS/EBIO 223 Prof. Rosenheim
– Specific heat: 0.24 cal·g1·oC-1 – Mass: 5 x 1018kg – 1.2 x 1021 cal (to inc. 1K) – 3.1 x 1023 cal (total)
Intro. Oceanography
Oceanic Heat Transport • N. Atlantic, with current continental configuration, can effectively pull equatorial heat into high latitudes
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Greenhous Feedbacks • Melting tundra, increased methane (+) • Warming oceans, melting sea ice, more productivity (-) • More NADW formation, more CO2 flux into deep ocean (+)
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography http://www.koshland-science-museum.org/exhibitgcc/historical02.jsp
6
Paleo-Greenhouse Effect? • Does CO2 lead or lag glacial/interglacial climate change? – Trigger is unknown, but strongest evidence keys on orbital cycles – Melting ice and rising seas change seawater chemistry and flow • CO2 degases
– Tundra melts • CO2 degases
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography http://www.koshland-science-museum.org/exhibitgcc/historical02.jsp
CO2 and the Oceans The oceans can be both a source and sink of CO2 • CO2 Sink – Cooler oceans – High productivity – Expose continental shelf
• CO2 Sources – Warming deep ocean – Destabilize deep ocean EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Greenhouse Gas Variability • Holocene (the period after the last glaciation) CO2 levels paint a vivid picture of recent CO2 increases • “Instantaneous” CO2 increase
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography IPCC
7
Greenhouse Gas Variability • Seasonal trends in CO2 persist due to temperate forests and phytoplankton blooms
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Sources for recent CO2 increase • Humans.
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Evidence for Human Sources • Carbon isotope composition of the atmosphere Direct Atmospheric Measurements
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
8
Archived Proxy Records of Anthropogenic CO2
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Earth’s Temperature Change • Average temperature of Earth hasn’t climbed as fast as CO2 levels • Our instrumental record is short (100 y), anything before that has a high uncertainty
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Why isn’t the temperature increase proportional to the CO2 increase? • 2 heat pumps – atmosphere and ocean • Oceans have more heat capacity than atmosphere • Verifiable changes in ocean circulation are the manifestation of this increased CO2.
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
9
Ocean Heat Content
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
New Data from the Caribbean Sea • Ocean climate change is not as straightforward as a global composite
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
New Data from the Caribbean Sea a. 30oN
B’
B
15oN
60oW
90oW Mann et al., 2004, global composite
0.5
1
1.5 o
b.
2
2.5
3
C/century
B
B’
0 36
Depth (m)
• Climate change in the largest heat sink of our climate system is regionally complex.
Sclerosponges 200
(Rosenheim et al., 2005)
36
400
80oW
35.2
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
70oW
35.4
60oW
35.6
35.8
50oW 40oW Longitude 36.0 36.2 36.4 Salinity (PSU)
30oW
36.6
20oW
36.8
37.0
10
Geologic Carbon Cycle • How does the earth lower the CO2 concentration in the atmosphere? – Natural sinks of CO2 • Biomass burial • Formation of CaCO3 • Tectonic burial/uplift of sediments
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Biogenous Sediment • CaCO3 is a CO2 sink
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Tectonic Carbon Sinks • Burial of CaCO3 sediments – Potential for volcanic evasion of CO2
• Uplift of sediments out of marine environment – Potential for weathering
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
11
Oceans’ Roles in the Carbon Cycle • • • •
Dissolution of CO2 Calcification Photosynthesis and metabolism 50X atm. CO2 in oceans
http://www.visionlearning.com/library/module_viewer.php?mid=95
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Carbon Sinks: Deep vs. Surface Ocean • Surface ocean is site of carbon flux between ocean and atmosphere – Upwelling, ocean is a source – Downwelling, ocean is a sink – Productivity Pump
• Deep ocean - ~40X the carbon reservoir – Solubility Pump – CO2 is very soluble in the deepest parts of the ocean EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Surface Ocean Productivity Pump • Biomass is created in photic zone • Biomass dies, and what is not recycled (eaten) at the surface falls to the deep ocean • Here most biomass is recycled (eaten). Small fraction of biomass is buried • CaCO3 deposition is also biogenous EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
12
Biomass Burial as Carbon Sink • Both marine (diatoms) and terrestrial (plants)
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Deep Ocean – Solubility Pump • More CO2 can remain in solution at – Low temperature – High pressure
• Deep ocean fits these criteria and has a very large volume All of our fossil fuels are about 1/10 of the deep ocean carbon content!
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Anthropogenic Effects on Pumps • Productivity Pump – Productivity pump may be diminished by ocean acidification as CO2 increases in atmosphere
• Solubility Pump – As temperature rises, especially in surface oceans, CO2 dissolution becomes less efficient (g/L) – But more overall CO2 will dissolve because more is available (total g)
• Net effect – decreasing pH (increasing acidity) of world oceans EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
13
CO2 Sequestration • How can WE get rid of CO2? – We need to control biomass accumulation and burial, and/or ocean chemistry (for biogenous carbonate formation), and/or plate tectonics – Or, we need to come up with alternatives that do not mimic known earth processes
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Iron Seeding Projects • Southern Ocean Iron (Fe) Experiment • Does iron fertilization lead to enhanced carbon sequestration? • John Martin – “Give me a trainload of scrap iron and I’ll give you another Ice Age.” http://www.mbari.org/expeditions/SOFeX2002/history&purpose.htm
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Iron Seeding Projects • Other projects – SOIREE, FeEx, SERIES
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
14
Iron Seeding Outcome • In most regions Fe is not the only limiting reagent for carbon sequestration • In Southern Ocean, a diatom and phytoplankton bloom was persistent and was buried to deep water along an oceanic front • It would be difficult to count on Fe seeding to sequester all of our carbon EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
What about changing sources?
EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
Key Concepts • Main sources and sinks of CO2 • Oceans’ roles in the carbon cycle • Temperature change vs. CO2 increase – Why the heterogeneity?
• Carbon sequestration – Fads, fables and facts
• What can you do? EENS/EBIO 223 Prof. Rosenheim
Intro. Oceanography
15
