Saturday, March 20, 1999
Moderator: William Douros, Superintendent, Monterey Bay National Marine Sanctuary
Norman Hoffmann, Meteorologist-in-Charge
Almost 2/3 of the earth is covered by water. Moisture from the oceans is transported by winds aloft over land masses and deposited in the form of rain and snow supplying water for many uses. As the Science of Meteorology has improved, it has become known that circulation patterns over the Pacific Ocean influence weather over North America, along the west coast and especially in the winter. Surface pressure patterns over the South Pacific are indicators of impending changes in low level circulation patterns and thus the development of El Niño or La Niña or warmer than normal or colder than normal water over the central pacific ocean. Both El Niño and La Niña, which are oceanographic events have effects on atmospheric circulations, especially if they are strong events. These temperature anomalies in ocean temperature can produce significant changes in atmospheric circulation. The 1997/1998 rainy season was significant along the Central Coast and had the weather patterns had a significant effect on the Monterey Bay. Rainfall was higher, water temperatures were warmer and runoff was much higher.
Dr. Gary Griggs
Although historic records of the effects of El Niño (ENSO) on marine productivity and the fishing industry off Peru have been documented for over four centuries, it has only been since the severe El Niño event of 1982-83 that residents of the central coast have become aware of the significance and impact of these recurring events. The 1997-98 event was a second reminder of the potential impacts of ENSO occurrences and, while forecast well in advance as a result of sophisticated satellite and oceanographic monitoring techniques, there was little that was done or could be have done to lessen the shoreline impacts. A careful analysis of historic coastal storm damage throughout this century has shown that ~75% of the major damaging storm events have taken place during ENSO events. Elevated sea levels, larger than normal waves, and heavier than normal precipitation all occur during El Niño events which are believed to be the major coastal hazard impacting the central California coast, and one which can be expected to recur for centuries to come.
Kathryn A. Zagzebski, Manager, Stranding Department
Climate changes influence marine mammal strandings in a variety of ways. The phenomenon of El Niño occurs when warm ocean currents replace cold water upwellings along the east Pacific Coast. Effects of El Niño include increased rainfall, storms, and changes in distribution of prey. During El Niño years, the number of marine mammal strandings increases dramatically. Types and age classes of species may vary, as may the problems causing strandings. This presentation compares marine mammal strandings handled by The Marine Mammal Center, a private, non-profit rehabilitation center in central California, during an El Niño year and non-El Niño years.
Market squid (Loligo opalescens) range from southeast Alaska to Baja, California, with the highest population concentrations south of San Francisco. Monterey Bay is a prime Pacific fishing ground for market squid. Historically total squid landings have fluctuated greatly. In some years the squid fishery has been the largest and most profitable fishery in the Monterey Bay area. For example, in 1994 landings reached the highest level since 1946. A total of 35.8 million pounds of squid worth over $5.2 million was landed at the ports in Monterey Bay during 1994. During El Niño years landings have decreased drastically. In 1983-1984 a low of one million pounds was landed, and in 1998 no squid were caught in Monterey Bay. The speaker, Dave Crabbe has fished commercially for twenty two years beginning in 1997 as a crewman fishing for blackcod out of the Monterey Harbor. In 1980 he purchased a 40-foot wood boat and began fishing for squid in the Monterey Bay. He now owns a 70-foot steel purse seiner, the Buccaneer, and fishes for squid along the coast from Los Angeles to San Francisco, as well as for sardines, anchovies, and mackerel in Monterey Bay. He also fishes for salmon in Alaska and herring in San Francisco Bay.
Dr. Stephen L. Eittreim, Roberto J. Anima, Andrew Stevenson and Jingping Xu
In order to understand the links between the seafloor geology and biological habitats of the Monterey Bay National Marine Sanctuary, the US Geological Survey has acoustically swath-mapped the Monterey Bay Shelf from the nearshore out to 150 m depth. We have mapped bedrock outcrops, coarse sand deposits, lineations related to the tectonic effects of active faults, and hard-grounds, perhaps related to seepage of sub-bottom waters and the resultant chemical precipitations on the seafloor. Most of the inner-shelf bedrock exposures can be correlated to exposures that occur in the coastal cliffs and roadcuts from northwest of Santa Cruz along route 1 to south of Monterey. These seafloor outcrops are erosional remnants that rise above the modern sediments of the continental shelf and must have stood well above the surrounding coastal plain during the time of lowered sealevel 12,000 years ago. A large percentage of the outer-shelf seafloor consists of outcrops of the Purisima Formation, an upper Miocene to Pliocene sedimentary sequence exposed along seacliffs and uplifted marine terraces above Santa Cruz and Watsonville. Large patches of medium to coarse sands are common on the inner to mid shelf. These sands may be the remnants of a 10,000-yr-old transgressive lag deposit, seen in windows through the thin surficial modern sediment. The medium to coarse sands are found within flat-floored 1-m-deep troughs in the form of large 1-m wavelength sand waves, that are kept mobilized seasonally by the large winter storm waves. This seasonal mobilization is believed to inhibit the deposition of finer sediments. Granitic rocks that make up the Monterey Peninsula are also seen as acoustically-distinctive outcrops on the continental shelf around the Peninsula out to depths of from 80 to 100 meters.
Dr. Baldo Marinovic, Dr. Don Croll, and Scott Benson
We have been surveying the pelagic ecosystem of the Monterey Bay National Marine Sanctuary Coastal Upwelling Center (MBNMS-CUC) for the past three years as part of an integrated study of seasonal and inter-annual variability in ecosystem dynamics and their corresponding effects throughout marine food webs. The recent 1997/98 El Niño provided us with a unique opportunity to study, in previously unprecedented detail, the impacts such acute climactic events have on pelagic ecosystems. These impacts can occur on a variety of spatial and temporal scales and can affect a variety of phenomena ranging from physical oceanographic processes to apex predator (e.g. seabirds and whales) responses. Our data suggest that while there were clear and dramatic impacts on phytoplankton and zooplankton production that resulted from the recent El Niño event, they were less dramatic in the MBNMS-CUC then in the offshore, oceanic ecosystems of the California coast. Consequently, coastal upwelling systems such as the MBNMS-CUC may serve as important refuges for a variety of organisms during periods of environmental stress. These results provide new insights into how coastal-upwelling ecosystems may respond to more gradual patterns of climate change. Furthermore they dramatically emphasize the need for careful management of these valuable environmental resources.
Dr. Marlene Noble, Physical Oceanographer
The coastal waters off central California that stretch from Pt. Reyes southeastward to Año Nuevo are unique. The shelf offshore San Francisco is the widest on the western US border, yet it narrows abruptly to the south and disappears off Monterey, where the largest west coast submarine canyon, Monterey Canyon, cuts across the shelf and slope into the deep ocean basin. Not surprisingly, these abrupt changes in topography severely impact the circulation patterns in the region, altering the transport of water, nutrients and suspended materials. Currents on the narrow Monterey shelf interact more strongly with oceanic flows than currents on the wider, more wind-driven Farallon shelf. The abrupt steepening of slope topography just north of the Farallon Islands causes the normal poleward flow that tends to hug the shelf-break to turn offshore, into the deeper ocean. Tidal currents not only have widely different amplitudes in this region, but they also change frequency. Off San Francisco, the daily tidal currents are enhanced so that they are stronger than predicted by the astronomical tides. Tidal currents within numerous submarine canyons are strong enough to erode canyon walls, causing material to move from the shelf toward the deep ocean. In many ways, the shape of our unique topography controls local changes in the currents and sediment transport patterns.
90 sites were surveyed along California and Baja, to determine at what spatial scale El Niño driven storms affected giant kelp communities. These sites spanned the entire geographic range of the giant kelp Macrocystis pyrifera in the Northeast Pacific, and were surveyed for giant kelp density just before, immediately following and several months after this recent El Niño. Interspersion of survey sites allowed community changes to be compared among spatial scales ranging from meters to thousands of kilometers. M. pyrifera populations in southern California and Baja were severely depleted during this event while central California populations were relatively unaffected. Recoveries of the southern populations were highly variable among nearby locations within each of these regions. Comparisons with previous El Niños indicated that the driving factors behind their effects on giant kelp forests were; wave intensity in central California, and the synergism between ocean temperature and the timing of storm events in southern California.