Use of an ion exchange technique to measure copper complexing capacity on the continental shelf of the southeastern United States and in the Sargasso Sea

An ion exchange technique has been used to determine the copper complexing capacity (CuCC) of strong organic complexing agents at 21 stations across the continental shelf of the southeastern United States and in the western Sargasso Sea. The concentration of dissolved organic carbon (DOC) and total particulate materal (TPM), two pools of potential complexing agents, was also measured at each station. The CuCC ranged from 0.014 to 1.681 μM Cu dm⁻³ on the inner shelf, from 0.043 to 0.095 μM Cu dm⁻³ in mid and outer shelf waters, and from < 0.010 to 0.036 μM Cu dm⁻³ at the Sargasso Sea stations. The correlation between CuCC and both DOC and TPM is highly significant (α < 0.01). Two synoptic surveys of the distribution of DOC and TPM across the shelf showed that DOC ranges from > 3 mg C dm⁻³ nearshore to <1 mg C dm⁻³ offshore and that TPM ranges from > 50 mg dm⁻³ nearshore to <1 mg dm⁻³ offshore. Both TPM and DOC are most variable on the inner shelf. These data are consistent with CuCC data which indicate that the CuCC of inner shelf waters was relatively high and very heterogeneous. In contrast, DOC, TPM and copper complexing capacity are low and nearly invariant at the Sargasso Sea stations. We present a model of the distribution of complexing agents in different marine environments and hypothesize that the mechanisms underlying differences between environments relate to differences in the source(s) and nature of complexing agents in each system.     

Modelling of run up of steep non-breaking waves

A Navier–Stokes solver is used to examine steep waves as they run up a steep beach (10.54°). The volume of fluid method (VOF) is used to model the free surface. Comparison with experimental results shows reasonable overall agreement in the prediction of the free-surface, velocities and accelerations within the flow. A spurious feature at the free-surface was found which does reduce the quality of the results. For a steep wave we see the transition from a steep wave front to a smooth run-up tongue at the beach that is in qualitative agreement with experiment.     

International refugees: a geographical perspective

In the modern era, the world's refugee problem has changed magnitude and location; it has expanded from a local to a continental, and now global, scale issue. About 90% of the world's 10 million refugees are from developing countries, and over 90% of these will stay there. Refugee generating and receiving countries are concentrated in 5 world regions: Central America, Southwest Asia, Southeast Asia, and Sub-Saharan Africa. Each concentration is unique and is associated with a particular set of regional conflicts. International efforts address short-term relief needs, whereas political instability and repression that generate refugees continue unabated. Refugees along sensitive border regions affect bilateral relations, large groups of refugees can pose political and security problems for the host country, and disputes over refugee policies and their implementation can complicate diplomatic ties. Some highlights of the data follow. 1) The 3 million cross-border refugees and 5.5 million internally displaced persons make the many governments in Sub-Saharan Africa increasingly dependent on Western assistance to solve their problems. Refugees are fleeing armed conflict, tribal violence, and drought, and often generate additional regional turmoil. 2) 3-4 million Afghans have fled their country since the 1978 Marxist coup; about 2.5 million have entered Pakistan. Most choose to remain in camps near the Afghanistan border where they are targets of cross-border attacks. 3) 1.2 million Salvadorans, Guatemalans, and Nicaraguans live outside their native countries. Official refugee and unofficial migrant populations are active in various rebel insurgencies, contribute to strained bilateral relations and tensions in border areas, and are the subject of heated political debate in host countries. 4) 90% of the 1.7 million Indochinese who fled from 1975-May 1986 have been resettled; 168,000 refugees remain in 1st-asylum camps, not including 240,000 Khmer without refugee status, in temporary camps in Thailand. Thailand's large refugee population is involved in factional strife, smuggling, and guerrilla activities. The Thai are particularly concerned about Hmong refugees, who are accused of opium cultivation and destruction of Thai forests through slash-and-burn cultivation. 5) Nearly 62% of the thousands of present Vietnamese refugees to Hong Kong have been in camps 3 years, and 17% 6 years. Many have turned to crime, alcohol, drugs, or prostitution.     

Application of a coupled ice‐ocean model to the Labrador Sea

Abstract

The steady, coupled ice‐ocean circulation model of Willmott and Mysak (1989) for a meridional channel is applied to the Labrador Sea for the winter season. The model consists of a thermodynamic reduced‐gravity ocean combined with a variable thickness ice cover that is in thermal equilibrium. Upon specifying the forcing fields of surface air temperature, wind stress and water temperature along the open southern boundary, the winter climatological ice‐edge position, ice thickness, ocean circulation and temperature fields are determined in the channel domain. The sensitivity of the results to the various model parameters is examined. In particular, the optimum heat exchange coefficients for the interfaces of air‐water, ice‐water and air‐ice are found.

The model ice‐edge position compares favourably with the 50% winter climatological ice concentration isoline obtained from an analysis of 32 years (1953–84) of sea‐ice concentration data. The simulations of the ocean temperature and ice thickness are also quite realistic according to the observed records available. The model is also applied to two specific winters (1981 and 1983) during which anomalous sea‐ice and weather conditions prevailed in the Labrador Sea.