Origin and Pathway of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint

The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13 degrees C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13 degrees C Water lies well outside the tropics. In the South Pacific, some 13 degrees C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water's origin. The South Pacific origin of the 13 degrees C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13 degrees C Water (25.8 < sigma(theta) < 26.6 kg m(-3)) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13 degrees C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above sigma(theta) = 25.8 kg m(-3) and 34.6% from depths below sigma(theta) = 26.6 kg m(-3), indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13 degrees C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.

Relationship between the ennoblement of passive metals and microbe adsorption kinetics in seawater

The relationship between microbial colonization of two kinds of passive metals and ennobling of their corrosion potentials (E-corr) were studied. Two types of passive metal coupons were exposed to natural seawater for about ten days. Under laboratory conditions, all corrosion potentials of the samples ennobled for about 200 mV. Epifluorescence microscopy showed that bacteria adsorption was the main process during about the first day immersion and bacteria reproduced in the following days. The bacteria number increased on the metal surface according to an exponential law and the kinetics of bacteria adsorption at the metal surface during this period was proposed. The ennoblement of E-corr was similar to the increasing bacteria number: E-corr increased quickly during the bacteria adsorption process and increased slowly after biofilms had formed.