Ocean models/modeling challenges

The backbone of the climate forecast, of course, is the operational model that links the short-term El Nino scale to the longer term. The observing system is the key challenge for testing the veracity of calculations. Carbon sources and sinks have been discussed. I believe that upper ocean observations, climate data records at the surface, and benchmark observation that establish the long-term evolution of the climate in an absolute sense constitute the centerpiece of what must be done. 

Original estimates of carbon export in the Southern Ocean based on the iron-induced efficient utilization of nitrate suggest that as much as 1.8 x 10 t of carbon could be removed annually (Figure 10). These estimates of carbon sequestration have been challenged by some modelers yet all models lack important experimental parameters which will be measured in upcoming experiments. 

It must be realized that a state must be reached where experiments and theory go hand in hand, leading to the development of better (more realistic) models, and acquisition of critical tracer data. In the absence of a knowledge of the processes involved, models employed often yield very erroneous results. Thus, whereas even a few tracer data are quite informative (since a few data points can be treated only with zero order models), any attempts to understand oceanic processes in detail pose a serious challenge. A few examples are considered here, where tracer data have contributed to the development of realistic models. As mentioned earlier, simple one-dimensional models were developed earlier on using two parameters K and w, to consider vertical transfer of tracers through an oceanic column. Even today these are used, in the absence of better alternatives, and in reality, because of a lack of tracer data in the three-dimensional space. The result is that as yet the general validity of the K-w models in space is not known or their dependence on climate. The latter arises because there are experimental tracer data for ocean waters only during the Holocene. 

When the organism dies the skeleton falls to the bottom of the ocean. Many of these skeletons have shapes similar to bubbles trapped in frameworks. Some of the Radiolarian skeletons are shown in Fig. 4.24. These skeletons were obtained by the biologist Ernst Haeckel on the Challenger Expedition of 1873-76. He found the skeletons in samples of mud taken from the ocean bed. Many of the samples are to be found in the Natural History Museum, London, England. Some superb glass models of these skeletons are to be seen at The Natural History Museum in New York City. 

Defining a representative composition for the ocean end-member in the models is particularly challenging because nearly every aspect of the physical and chemical state of the coupled ocean/atmosphere system on the early Earth (temperature, pH, elemental composition, salinity, oxidation state, etc.) is poorly understood at present and continues to generate vigoroits debate. We adopt an ocean composition that appears consistent with the cirrrently available corrstraints. The composition of the model late Hadean seawater nsed in this cormnitrrication is given in Table 1. 

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