William C. Patzert

On the Characteristics and Circulation of the Southwestern Atlantic Ocean

Abstract The waters found within the southwestern Atlantic Ocean extend into it as separate lavers with markedly different characteristics. Along the western boundary the deeper waters, derived from the North Atlantic, are warm, highly saline, oxygen-rich and nutrient-poor. This North Atlantic Deep Water (NADW) lies within the density range of the Circumpolar Water (CPW) from the south, which is cooler, lower in salinity, very low in oxygen and very high in nutrients. Where the NADW and CPW meet in the southwestern Atlantic, the NADW separates the CPW into two layers above and below the NADW—each less saline, richer in nutrients and lower in oxygen than the NADW. Above the upper branch of the CPW lies the Subantarctic Intermediate Water, which is lowest in salinity of all the layers. Beneath the lower branch of the CPW lies an abyssal layer derived from the mid-depths of the Weddell Sea. It is colder, less saline, lower in nutrients and higher in oxygen than the Circumpolar Water. These layers appear to b...

Predicting and Observing El Niño

In October 1974 the occurrence of a weak El Ni�o event was predicted for early 1975 on the basis of the southern oscillation index. An expedition was organized to observe the event in the waters off Peru and Ecuador during two cruises in order to study its occurrence and its development with time. During the first cruise a massive transgression of warm low salinity water across the equator to 4�S was observed, as well as a depression of the thermocline along the equator and off the coast of South America, indicating the start of El Ni�o development. During the second cruise the oceanographic situation had changed and conditions were returning to normal.

Recent hiatus caused by decadal shift in Indo-Pacific heating

Looking for the missing heat Global warming apparently slowed, or even stopped, during the first decade of the 21st century. This pause is commonly called the “hiatus.” We know, however, that Earths climate system is accumulating excess solar energy owing to the build-up of greenhouse gases in the atmosphere. Where, then, has this energy gone if not into the air? Nieves et al. find that over this period, the surface Pacific Ocean has cooled but the upper Indian and Southern Oceans have warmed. Thus, the decade-long hiatus that began in 2003 would appear to be the result of a redistribution of heat within the ocean, rather than a change in the whole-Earth warming rate. Science, this issue p. 532 Shifting ocean heat distributions slowed global warming. Recent modeling studies have proposed different scenarios to explain the slowdown in surface temperature warming in the most recent decade. Some of these studies seem to support the idea of internal variability and/or rearrangement of heat between the surface and the ocean interior. Others suggest that radiative forcing might also play a role. Our examination of observational data over the past two decades shows some significant differences when compared to model results from reanalyses and provides the most definitive explanation of how the heat was redistributed. We find that cooling in the top 100-meter layer of the Pacific Ocean was mainly compensated for by warming in the 100- to 300-meter layer of the Indian and Pacific Oceans in the past decade since 2003.

Heat Waves in Southern California: Are They Becoming More Frequent and Longer Lasting?

Los Angeles is experiencing more heat waves and also more extreme heat days. These numbers have increased by 3.09°F (1.72°C) per century and 22.8 per century occurrences, respectively. Both have more than tripled over the past 100 years as a consequence of the steady warming of Los Angeles. Our research explores the daily maximum and minimum temperatures from 1906 to 2006 recorded by the Department of Water and Power (DWP) downtown station and Pierce College, a suburban valley location. The average annual maximum temperature in Los Angeles has warmed by 5.0°F (2.8°C), while the average annual minimum temperature has warmed by 4.2°F (2.3°C). The greatest rate of change was during the summer months for both maximum and minimum temperature, with late fall and early winter having the least rates of change. There was also an increase in heat wave duration. Heat waves lasting longer than six days occurred regularly after the 1970s but were nonexistent from the start of 1906 until 1956, when the first six-day heat wave was recorded. While heat days have increased dramatically in the past century, cold days, where minimum temperature is below 45°F (7.2°C), show a slight decreasing trend.

Anticyclonic Flow Around the Hawaiian Islands Indicated by Current Meter Data

Abstract The resultant flow calculated from 42 current meter measurements near the Hawaiian Islands for different periods of from two to six weeks between October 1964 and May 1969 indicate nearshore anticyclonic circulation around the Islands. Two possible mechanisms generating this flow are considered: steady currents induced by oscillations around the Islands and the cyclonic shear imposed on the local trade winds by the Islands.