Final Flashcards
How can we measure groundwater changed across the globe?
Satellites
What is GRACE?
Twin satellites launched in 2002 (ended in 2017), joint mission between NASA and German Aerospace center
How does GRACE measure water change?
1.) Satellites follow each other on the same orbit
2.)First satellite moves towards mass on Earth and is puled increasing distance between satellites (Distance is proportional to the mass **water)
3.) Over time change in distance between satellites in an area tells us how mass of water has changed.
How much carbon was released into the atmosphere from combustion of fossil fuels and land use change from 1750-2019?
700+/-75 PgC (1PgC=1015g of Carbon)
How much of this carbon remains in the atmosphere today?
less than half
How is net accumulation of GHGs in the atmosphere controlled?
Biogeochemical processes that exchange carbon between the atmosphere and multiple reservoirs on land and in oceans.
What percentage of carbon was taken up/absorbed by different earth systems?
46% accumulated in atmo
23% taken up by the ocean
31% stored by vegetation in terrestrial ecosystems
Airborne fraction
the fraction of anthropogenic CO2 emissions that has accumulated in the atmosphere
What does the calculated airborne fraction suggest?
Land and ocean CO2 sinks have continued to grow at rate consistent with the growth rate of anthropogenic CO2 emissions
-however, interannual sub-decadal variability dominated by land sinks
What are uncertainties surrounding the airborne fraction?
1.) Large year to year variability because of natural climate modes and volcanic activity
2.) Uncertainty in the amount of CO2 emissions from land use change (makes total anthropogenic emission amount unclear)
Co2 Fertilization
The efficiency of photosynthesis increases in the presence of higher CO2.
As a result, plants can potentially increase biomass and land carbon uptake
What is the trend of CO2 fertilization for the future?
Expected to continue in this century and is the dominant cause for the projected increase in land carbon uptake
What is CO2 fertilization modulated by?
Acclimation of photosynthesis to long term CO2 exposure
Growth temp
Seasonal drought
Nutrient availability
What does the lack of free-air CO2 enrichment experiments in phosphorus-limited tropical forests limit?
The understanding of the role of phosphorus availability in constraining the CO2 fertilization effect globally
CO2 Physiological Forcing
Plants are able to meet their carbon needs without needing to open their stomata as wide when CO2 concentrations are higher because rate of CO2 diffusion into the plant through stomata depends on the gradient of CO2 between atmosphere and leaf interior
**reduction of transpiration
Water use efficiency (WUE)
the ratio of carbon assimilation (photosynthesis) to water lost by the plant through transpiration
What does increasing atmospheric CO2 concentration do to leaves?
Enhances photosynthesis and drives a partial closure of leaf stomata leading to higher WUE at the leaf canopy and ecosystem scales
What does leaf stomata closure effect?
Land freshwater availability because of reduced plant transpiration, leading in some regions to higher soil moisture and runoff
Plant CO2 water availability projections are subject to what ESM uncertainties?
Quantify transpiration, among them the correct representations of plant hydraulic architecture such as changes in xylem anatomical properties and deep rooting
How is Arctic Greening monitored?
From satellites since 1982 by the Advanced Very High resolution Radiometer (AVHRR) on NASAs polar orbiting satellites
How do satellites monitor greeness?
Measures reflectance signatures in discrete regions of the radiometric spectrum
-Vegetation absorbs visible light but strongly reflcects near infrared light
What is the total near-surface soil carbon for the northern circumpolar region?
1,035+/- 150 Pg C
How much does the permafrost region represent of global soil carbon?
33%
The permafrost region contains twice as much carbon as there is currently in the atmosphere
What is the rate of permafrost carbon release controlled by?
The overall decomposability of organic carbon as well as the presence of oxygen
What is permafrost carbon susceptible to?
Rapid breakdown upon thaw, not clear if it will be sustained on the decade-to-century time scale of climate change or what degree of variation exists within soils
How much carbon is released after a decade in aerobic conidtions?
1-76%
How much lower are anaerobic cumulative carbon emissions that aerobic soils?
75-85%
What are the CH4 values of the overall impact on climate over a 100-year timescale?
25% in mineral soils
45% in organic soils
What is the model estimate of potential carbon release from the permafrost zone?
37-174 Pg carbon by 2100
What is the effect of Ch4 losses from future permafrost zone?
increasing the warming potential of released carbon by 35-48% when accounting for CH4 over a 100 year timescale
What do models indicate increased plant carbon uptake will do?
offset soil carbon emissions from the permafrost region for several decades as climate becomes warmer
What do models indicate increased plant carbon uptake will do over longer timescales?
Microbial release of carbon overwhelms the capacity for plant carbon uptake, leading to net carbon emissions from permafrost to the atmosphere
How much carbon could be released with abrupt permafrost thawing?
60-100 billion tons of carbon by 2300
Arctic Amplification
refers to the enhancement of near-surface air temperature change over the Arctic relative to lower latitudes
What is Artic Amplification driven by?
-Local: snow, sea ice albedo, cloud and insulation feedbacks
-remote: atmo and oceanic heat transport, atmospheric moisture transport from the midlatitudes/tropics to the Arctic
Planck response
mechanism acting to stabilize the climate due to surface and tropospheric warming increasing and outgoing longwave radiation which opposes the effects of positive forcing
How does Planck response lead to AA?
it is weaker over the colder Arctic relative to lower latitudes and to the global mean
Large change in the greenhouse effect
when CO2 increase at low Co2 values
small change in the greenhouse effect
when CO2 increases at high CO2 values
Global Warming potential
measure of how much energy the emission of 1 ton of gas will absorb over a given period of time relative to the emission of 1 ton of CO2
How is GWP useful?
provides a common unit of measure, which allows analysts to add up emission estimates of different gases
allows for policymakers to compare emissions reduction opportunities across sectors and gases
What is CO2’s GWP value?
1
What is Methanes GWP value?
27-30 over 100 years
Bottom up emission estimates
multiplying average emission factors for each known source category by an activity factor for that source category to estimate the annual emissions from a facility or emission source
Top down emission estimates
regional scale, aircraft mass balance measured atmo methane concentrations are used in models to infer emission rates
How does TD compare to BU estimates?
TD is typically 1.5 times larger than BU
Why are BU estimates low?
inaccurate emission factors or underrepresented sources whose overall emissions are not adequately characterized by measurement campaigns employing systematic sampling
Montreal Protocol goal
Reducing CFC production 20% by 1993 and 50% by 1998
Topographic Uplift Oxygen Isotope example:
Going up the mountain:
1.) Air adiabatically expands/cools
2.) Cooling results in condensation
3.) 18O falls out and becomes less abundant
4.) Results in isotopic lapse rate
Weak rainfall events
dominated by heavier isotopes
strong rainfall events
dominated by lighter isotopes
Isotopic amount effect
Difference in rainout efficiency
indicates that there is a negative correlation between the amount of rainfall and the isotope ratio
Where are mass spectrometers used to measure the ratio of isotopes?
-Melted ice water from an ice core
-calcium carbonate shells on the ocean floor that record oxygen isotope conditions of ocean water at the time the shells are formed
Mass Spectroscopy
analytical tool that measures the mass to charge ratio of molecules in a sample
What are the uses of mass spectroscopy?
Used to identify unknown compounds by determining their molecular weight
Determine structures and chemical properties of molecules
4 stages of mass spectrometer
1.) Ionize the sample
2.) Accelerate the ions
3.) Deflect the ions
4.)Detect the mass/charges of the ions
Ionizing Sample
1.) Atom/molecule is prepared and ionised by knocking one or more electrons off to give positive ion
2.) Electrons can be knocked off is with a high energy electron beam
Accelerate the ions
ions are accelerated using an electric field created by electric plates
Deflect ions
1.) ions move through strong magnetic field
2.) magnetic field interacts with electric field of each ion causing ion to deflect
lighter ions are deflected more easier than heavier
Detect mass of ions
1.) metal plate intercepts the ion
2.) positive ion will attract an electron from metal plate causing small flow in electrions and is detected by electric current
Different paths detected by the plate correspond to different masses of the ion
End product mass spectrum
the mass of the ion divided by the charge of the ion
charge is usually 1, so you are looking at the mass
Nitrogen release and the oceanic crust
when the crust is subducted nitrogen is released into the rock above, either becomes locked up in the minerals or released to the atmo
How is nitrogen released through subduction zones?
The mantle is characterized by oxidized conditions, turns N into N2 which is degassed through volcanoes
**Only occurs in ocean subduction zones
When did atmospheric N2 levels resemble todays level?
3-3.5 Ga (billions years ago)
*Can be used as a way to constrain the start date of plate tectonics on earth
Nitrogen Cycle
1.) Atmo N enters ecosystems through bacteria (Nitrogen fixation)
2.)Converted by other bacteria and used by plants
3.) Returned to atmo via decompositon and is denitrified
Radioactive Decay
the process in which a radioactive atom spontaneously gives off radiation in the form of energy or particles to reach a more stable state
Parent Isotope
the atmoic nucleus of the unstable isotope that decays
Daughter Isotope
the product of the isotope decay
Half-Life
The amount of time it takes for half of the parent isotope to decay into daughter isotopes
Radiometric dating
compares the abundance of a naturally occuring radioactive isotope with the material to the abundance of its decay products
Why use Zircon?
1.) contains trace amount of uranium, allows for uranium-lead dating
2.) can survive geologic processes like erosion and metamorphism
3.) upon formation it strongly rejects lead
*Any accumulation of lead is directly the result of radioactive decay
Why is uranium-lead dating useful?
1.) the uranium-238 decays to lead-206
2.)uranium-235 decays to lead-207
Allows to cross check your age estimate in some material
Seismic tomography
Imaging technique that uses seismic waves generated by earthquakes or explosions to create 2D/3D dimensional images of Earth’s interior.
