We will call these flows the warm and cold biologic pumps and to begin with, they will simply be represented by constant flows of 6 Gt C/yr from the warm water, and 4 Gt C/yr from the cold surface water. Let's see if we can summarize this carbonate chemistry -- it is important to have a good grasp of this if we are to understand how the global carbon cycle works. In general, higher temperatures tend to correspond with higher rates of precipitation, so we can consider the affects of water to go hand in hand with temperature. And yet if we don't make some attempt to describe this process in the form of a global model, our understanding of the dynamics of the global carbon cycle will languish in the early stages. What controls the strength of this biologic pump? A great diversity of microorganisms live in the soil -- perhaps as many as 1000 species in a cubic centimeter -- and they are capable of consuming tremendous quantities of organic material. The concentrations of both the carbonate and bicarbonate ions can be expressed as a function of both the alkalinity and the concentration of total dissolved inorganic carbon, SCO2, as shown in the following: Here, we need to remember that this is an approximation because we ignored the term for H2CO3 in equation (8). On our dynamic planet, carbon is able to move from one of these realms to another as a part of the carbon cycle. The CO2 used in this process gets into the interior of the leaf through small openings about 10 microns in diameter called stomata, which the plant can control like a valve, opening and closing to adjust the rate of transfer. Another pathway for carbon to move from the sedimentary rock reservoir to the … If this were not the case, then the size of the land biota reservoir would be growing or declining, which may in fact be the case (it's doing both in different parts of the Earth), but we would like our model to be more or less in a steady state to begin with. In the form of an equation: where Fadv is the flow of carbon by advection and WarmSurfOc is the reservoir of carbon stored in the warm surface waters of the worlds oceans. Land-use changes other than deforestation can also add carbon to the atmosphere; agriculture, for instance, involves tilling the soil, which leads to very rapid decomposition and oxidation of soil organic matter. For the majority of plants, this upper limit is not likely to come into play given the kinds of temperature changes we might expect in the space of a couple hundred years, so we can safely ignore it here (if our model does lead to temperature changes of greater than 10-20°C in a hundred years, we would presume that there is some problem with the model as this is unrealistic behavior). Our goal is to find an expression for the concentration of H2CO3, so we begin by rearranging the equation on the left above (1) to the following form: Then we rearrange the right side of (1) so that it becomes: Next, we substitute (3) into (2), to give us our desired equation expressing H2CO3 in terms of HCO3- and CO32-. Different paths of the carbon cycle recycle the element at varying rates. This transfer is often referred to as the biologic pump, and it causes the concentration of CO2 gas, and also SCO2 , the concentration of total dissolved inorganic carbon in the surface waters to be less than that of the deeper waters. This decomposition thus returns carbon, in the form of CO2, to seawater. Some of the carbon, both organic and inorganic (i.e., calcium carbonate shells) produced by marine biota and transferred to the deep oceans settles out onto the sea floor and accumulates there, eventually forming sedimentary rocks. The movement of carbon from reservoir to reservoir is known as the carbon cycle. We get some help from the fact that the relative proportions of bicarbonate (HCO3-) and carbonate (CO32-) play an important role in establishing the balance of positive and negative charges in seawater. Since it's invention over 3 billion years ago, photosynthesis has been one of the most important processes on Earth, helping to make our planet different from all the other planets. These microbes (considered in terms of their respiratory output) are very sensitive to the organic carbon content of the soil as well as the temperature and water content, respiring faster at higher carbon concentrations, higher temperatures and in moister conditions (although if the soil is flooded with water, conditions are worse since no oxygen can get into the soil -- the majority of the microbes need oxygen to respire, as can be seen from the general equation for respiration given under the discussion of plant respiration).