Model Evidence for Interdecadal Pathway Changes in the Subtropics and Tropics of the South Pacific Ocean

Numerical simulations using a version of the GFDL/NOAA Modular Ocean Model （MOM 3） are analyzed to demonstrate interdecadal pathway changes from the subtropics to the tropics in the South Pacific Ocean. After the 1976 -77 climate shift, the subtropical gyre of the South Pacific underwent significant changes, characterized by a slowing down in its circulation and a southward displacement of its center by about 5°- 10° latitude on the western side. The associated circulation altered its flow path in the northwestern part of the subtropical gyre, changing from a direct pathway connecting the subtropics to the tropics before the shift to a more zonal one after. This effectively prevented some subtropical waters from directly entering into the western equatorial Pacific. Since waters transported onto the equator around the subtropical gyre are saline and warm, such changes in the direct pathway and the associated reduction in equatorward exchange from the subtropics to the tropics affected water mass properties downstream in the western equatorial Pacific, causing persisted freshening and cooling of subsurface water as observed after the late 1970s. Previously, changes in gyre strength and advection of temperature anomalies have been invoked as mechanisms for linking the subtropics and tropics on interdecadal time scales. Here we present an additional hypothesis in which geographic shifts in the gyre structure and location （a pathway change） could play a similar role.

Events of decadal thermocline variations in the South Pacific Ocean

The SODA data generated from a numerical model with data assimilation axe used to study the decadal thermal anomalies in the thermocline of the South Pacific. Three notable events of decadal thermocline variations are found. First, two major warm subduction events originated from outcrop regions centered at 30°S, 150°W in the South Pacific Ocean occurred between 1960s and 1980s propagating toward the western Tropics and at 30°S, 90°W in the late 1970s propagating directly toward the eastern Tropics. Second, a special westward warm event originating from the eastern boundary around 15°S occurred in the early 1980s. Thirdly, a distinct zonal location transition of the positive temperature anomalies near 10°S took place in the late 1970s. The results suggest that the warm events in the subtropical South Pacific region are important to the decadal variability of the western tropical Pacific before the late 1970s and to the eastern tropical Pacific after the late 1970s.

First record of Odontaster penicillatus populations(Philippi,1870)(Echinodermata:Asteroidea)in the Atacama and Antofagasta regions,Chile(Southeast Pacific)

We report for the first time the presence of local populations of the starfish Odontaster penicillatus in the regions of Atacama and Antofagasta,Chile.This finding indicates an extension of the distribution limit of 500 km with respect to the last observation made in 2007 in Isla Grande de Atacama.A total of 121 specimens of O.penicillatus were recorded at depths of between 8 m and 24 m.They were associated with rocky substrate and with different species of barnacles,sponges and bryozoans.The presence of O.penicillatus expands the knowledge of the benthic biodiversity of the region,and the development of studies on its ecological importance will be promoted.

MEDIUM-RANGE OSCILLATION AND TELECONNECTION OF THE ATMOSPHERIC CIRCULATION SYSTEMS OVER THE NORTHWEST PACIFIC AND SOUTH INDIAN OCEANS

This paper aims to demonstrate some characteristics of the 20-50 day oscillations of certain circulation systems in low latitudes during the northern summer seasons.The teleconnection between the variations of the Mascarene high and the Northwest Pacific high and its physical mechanism are studied.How the Mas- carene high plays an important role in the interaction between the atmospheric circulations of both hemispheres is discussed.