Antarctic region total

Figure 4.7. The mean vertical distribution of (a) alkalinity and (b) total CO2 concentration normalized to the mean world ocean salinity value of 34.78. NA = North Atlantic, SA = South Atlantic, NP = North Pacific, SP = South Pacific, NI = North Indian, SI = South Indian, and A A = Antarctic region. (After Takahashi etal., 1980b.)...

Fig. 11-9 (a) The vertical distributions of alkalinity (Aik) and dissolved inorganic carbon (DIC) in the world oceans. Ocean regions shown are the North Atlantic (NA), South Atlantic (SA), Antarctic (AA), South Indian (SI), North Indian (NI), South Pacific (SP), and North Pacific (NP) oceans. (Modified with permission from T. Takahashi et ah, The alkalinity and total carbon dioxide concentration in the world oceans, in B. Bolin (1981). Carbon Cycle Modelling," pp. 276-277, John Wiley, Chichester.)... 

Evidence for the contribution of the CIO + BrO interaction is found in the detection and measurement of OCIO that is formed as a major product of this reaction, reaction (31a). This species has a very characteristic banded absorption structure in the UV and visible regions, which makes it an ideal candidate for measurement using differential optical absorption spectrometry (see Chapter 11). With this technique, enhanced levels of OCIO have been measured in both the Antarctic and the Arctic (e.g., Solomon et al., 1987, 1988 Wahner and Schiller, 1992 Sanders et al., 1993). From such measurements, it was estimated that about 20-30% of the total ozone loss observed at McMurdo during September 1987 and 1991 was due to the CIO + BrO cycle, with the remainder primarily due to the formation and photolysis of the CIO dimer (Sanders et al., 1993). The formation of OCIO from the CIO + BrO reaction has also been observed outside the polar vortex and attributed to enhanced contributions from bromine chemistry due to the heterogeneous activation of BrONOz on aerosol particles (e.g., Erie et al., 1998). 

Figure 1. This graph shows the rapid variation of CIO and 03 as the edge of the chemically perturbed region in the Antarctic polar vortex is penetrated by the National Aeronautics and Space Administration (NASA) ER-2 high-altitude aircraft over the Palmer Peninsula of Antarctica on September 16, 1987 (5). It is one of a series of 12 snapshots, or individual flights, during the Airborne Antarctic Ozone Experiment (AAOE) that show the development of an anticorrelation between CIO and 03 that began as a correlation in mid-August. When these two measurements are combined with all the others from the ER-2 aircraft, the total data set provides a provocative picture of how such chemistry occurs and what it is capable of doing to ozone.

The global natural flux of sulfur compounds to the atmosphere has recently been estimated to be about 2.5 Tmol yr1 (1) which is comparable to the emissions of sulfur dioxide (SO2) from anthropogenic sources (2). A substantial amount of the natural sulfur contribution (0.5-1.2 Tmol yr1) is attributed to the emission of dimethylsulfide (DMS) from the world s oceans to the atmosphere (3.4). One of the major uncertainties in this estimate is due to a scarcity of DMS and other sulfur data from the Southern Hemisphere, particularly the Southern Ocean region between about 40°S and the Antarctic continent, which represents about one fifth of the total world ocean area. 

Measured size distributions of salt particles are monomodal and can by parameterized by the power law, with the index varying within 0.97-4.2 (average 2.3-2.6). The density of MSA particles is close to 2.35 — 2.40 g/m The spatial distribution of Cn MSA (r > 1 pm) for different regions of the world ocean can be illustrated by the following values in the Pacific Ocean Cn = (1.2-1.5) cm in the Indian Ocean (0.9-1.0) cm" near the Australian coastline 0.4 cm near the boundaries of the Antarctic ice sheet (1.8-2.1) cm" and near the Black Sea coastline (0.32-1.93) cm" [8]. The vertical distribution of Cn MSA has some specific features. A maximum of Cn distribution is often observed at altitudes of several hundred meters (apparently, because of a decrease in the Cn MSA near the water surface, resulting from the capture of salt particles by sea waves). At altitudes 2-3 km the value of Cn MSA constitutes < 1 % of the total Cn value, which is explained by the cloud filter . However, over land, near the coastline, at an altitude of 3 km, Cn MSA is somewhat higher than at the same level over the sea surface. This is connected with a more intensive turbulence over land. In general, sea-salt aerosol particles have to be chemically composed of dried sea water 88.7% chlorides, 70.8% sulfates, 0.3% carbonates, and 0.2% other salts. 

Direct measurements of N uptake by heterotrophic bacteria in the Southern Ocean have only been conducted in the coastal waters of the northern Gerlache Strait region of the Antarctic Peninsula (Tupas et al., 1990, 1994). They determined that during a rich phytoplankton bloom, bacteria (<0.80 pm filtrates incubated in the dark) were responsible for 8—25% (mean = 17%) of the total community uptake. 

Based on measurements of the total column ozone content of the atmosphere from the ground as well as from satellites, a consistent picture of the current loss of stratospheric ozone can be derived. The most recent results are discussed in ref. [3]. Relative to the values in the 1970 s, the ozone loss at the end of the 1990 s is estimated to be about 50% in the Antarctic spring, where the ozone hole appears every year, and about 15% in the Arctic spring. In the mid-latitudes of the Southern hemisphere the loss is about 5% all the year round, while in the Northern hemisphere it is about 6% in winter/spring and about 3% in sum-mer/fall. No significant trend in ozone has been found in the Equatorial regions. In the second half of the 1990 s relatively little change in ozone has been observed in the mid-latitudes of both hemispheres. 

Figure 6.9. Observations of total ozone at various locations. The Antarctic data are from Halley (Farman et al., 1985 Jones and Shanklin, 1995) and updated courtesy of J. Shanklin. The Arctic data are from satellite observations described in Newman et al. (1997), updated courtesy of P. Newman. The Arosa, Switzerland, dataset is the longest running in the world (Staehelin et al., 1998a,b). Satellite observations from a slightly higher mid-latitude region are shown for comparison (Hollandsworth et al., 1995), updated courtesy of R. Nagatani. The satellite data are zonally and monthly averaged, while the ground-based data at each site have also been averaged over time as indicated in each case. Adapted from Solomon (1999).

Figure 6.16. Observations of the year-to-year variations in the size of the Antarctic ozone hole based on satellite observations of the region where total ozone drops below 220 Dobson Units. Figure courtesy of P. Newman (personal communication).

On a global scale, ground-based and satellite observations show significant decreases of total column ozone at middle latitudes in the northern hemisphere of 2.7% per decade in winter, 1.3% decade in summer, and 1.2% per decade in the fall. Similar decreases are apparent at middle latitudes in the southern hemisphere and at high latitudes, beneath the region of the Antarctic ozone hole, the decreases are 14% per year. The decreases have occurred primarily in the lower stratosphere. No trends in ozone concentrations have been observed in the tropics. 

A recent review on primary production estimates in ice-covered regions, based on standing stock and productivity data indicate that 25% of the total Arctic primary production takes place in sea ice (Table 2). In the Antarctic, the proportion of primary production taking place in the ice is even higher (33%) (Legendre et al. 1992). It is also worth noting that they estimated the production under ice in the Antarctic to account for less than 1% of the total primary production. 

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