1) The fish tank below is divided in the middle, with cooler and fresher water on
the one side, and warmer and saltier water on the other. If you remove the partition
from this tank, which of the original two water masses will float on top, and which
will sink to the bottom of the tank? Please explain your answer.
2) Because an atmosphere with CO2 and other greenhouse gasses absorbs and
reradiates some of the otherwise space-bound "Earthlight" back to Earth, the Earth’s
will warm if we add more greenhouse gasses to its atmosphere. Calculating just how
much warmer is a little complicated, but Archer has provided a pretty sophisticated
but easy to use online model that will calculate this for you. The model determines
the "Equilibrium near-surface air temperature" (i.e. ground temperature) based on a
number of parameters that can be adjusted.
For this question, you will change the pCO2, called the "CO2 mixing ratio", which is
located on the left-hand panel of the model. The "Equilibrium near-surface air
temperature" is calculated for a given pCO2 value and displayed on the upper right
hand panel (after you press the "Do it!" button; you'll get a lot of plots and
information here but just pay attention to the "Equilibrium near-surface air
The purpose of this exercise is to determine how much the ground surface would
warm with changing CO2 (and CH4).
a) Use the model to calculate the ground temperature (in °C) for 280 ppm CO2
and 0.6 ppm CH4 – these are the "pre-Industrial" concentrations. Now
calculate the ground temperatures for 380, 480 and 580 ppm pCO2, leaving
b) Is the temperature increase the same for each 100 ppm pCO2 increase?
Please explain your observation.
The current pCO2 level is about 406 ppm. How much has the surface warmed
according to this model with these parameters since the Pre-Industrial
period, and how does this compare with observations? If observations are
different from this estimates value, what could be the reason?
c) We haven't taken into account the current high methane (CH4) levels, which
are now about 1.8 ppm. Enter this number now into the model and calculate
the change in ground temp from preindustrial conditions (i.e. CO2=280 ppm
and CH4=0.6 ppm).
d) How much might climate warm in addition to your answer (d) 50 years into
the future if CO2 emissions continue at the current 1.5 ppm/year increase,
and methane emissions at the current average 7ppb/year increase (note the
difference in units: ppb and ppm)?
e) Add answers c and d together and this would be the total temperature
change from the preindustrial period to a time 50 years into the future – this
is one estimate for the future warming. Do you think this is an underestimate,
or an overestimate of the future warming, why?
3) Carbon is stored in many sinks on Earth.
a) List in increasing order the amount of carbon stored in the following
sinks: atmosphere, land (including biological organisms and soil), ocean.
b) Describe (with chemical equations) two processes through which
anthropogenic carbon dioxide gets taken up by the oceans. How do each
of these processes affect ocean pH?
c) If there were a sudden decrease in the concentration of atmospheric
carbon dioxide, over what timescales would you expect the (i) surface
ocean, (ii) deep ocean, and (iii) sediments at the bottom of the ocean to
reflect that change?
4. Proxies for past climate change allow scientists to reconstruct the Earth’s climate
history farther into the past than temperature measurements.
a) Name two proxies that are sensitive to Earth’s climate history. Describe why an
increase or decrease in each type of proxy measurement is associated with an
increase or decrease in the climate parameter to which the proxy is sensitive.
b) This figure from Mann et al., 2008 shows multiple temperature reconstructions.
What is notable about temperature changes (e.g., warming, cooling) ~1500-1800
AD? Describe the trend since ~1970. Please also approximate the magnitude of
temperature change in your answers.
c) Name three processes that might explain observed variations in Earth’s
temperature before the industrial revolution, and whether we would expect each to
increase or decrease average temperatures. Based on the timescales over which
each of these processes influences temperature, which would you not expect to be
associated with the temperature change observed ~1500-1800 AD?
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This will develop the condition of stratification.
For stable stratification to occur, density increases as depth increases in this case heavy fluid is on bottom of light fluid. i.e. More dense fluid is always at the bottom of light fluid. This is normal condition. For unstable stratification to occur, density decreases as depth increases in this case heavy fluid is at the top of light fluid. i.e More dense fluid is always at the top of light fluid. This is unstable condition.
Double diffusion and salt fingering:
Interestingly, even though, water column may be stably stratified at a particular time, instability may develop because diffusivity rate for heat and salt are different.
As a result is that if two water mass of same density but different combination of T & S ware in contact, one above the other, the differential (“double”) diffusion of these properties may give rise to density changes which render the layers unstable...