November 30, 2012

MBARI research presentations at the 2012 Fall Meeting of the American Geophysical Union (AGU)

Researchers from the Monterey Bay Aquarium Research Institute (MBARI) will present 21 different talks and posters at the American Geophysical Union Fall Meeting in San Francisco during the week of December 3 to 7, 2012. This page highlights a few of these presentations. A complete list of MBARI presentations is at the bottom of the page.

chimney-perspective-crop-200Ground-breaking expedition creates first detailed map of an entire deep-sea spreading center

Mapping an entire mountain range in three weeks would be quite an achievement for a land-based geologist. It is even more of a challenge when the mountain range is 2,300 meters (7,500 feet) below the ocean surface. In this case, the mountain range is the 50-km-long (32-mile-long) Alarcón Rise–an active volcanic spreading center at the south end of the Gulf of California. During spring 2012, MBARI researchers used two different types of undersea robots to study the Alarcón Rise in unprecedented detail. First they mapped the entire ridge using an Autonomous Underwater Vehicle (AUV), documenting features as little as 20 cm tall. Then they used the remotely operated vehicle (ROV) Doc Ricketts to collect videos, chemical data, sediment cores, and over 100 rock samples from all along the rise. In the process, they discovered over 100 hydrothermal chimneys and dozens of previously unknown deep-sea vent communities. They also discovered an enigmatic underwater volcano whose “rhyolitic” lavas are more closely related to those of Mount Saint Helens than to typical mid-ocean ridge basalts. These and other findings of MBARI’s Alarcón Rise expedition will be described in five AGU presentations:

Geology of the Alarcón Rise Based on 1-m Resolution Bathymetry and ROV Observations and Sampling
David A. Clague Thu 16:45 MS 306 T44A-04 (talk)
Morphology of the Alarcón Rise spreading axis from 1-m resolution AUV bathymetry surveys
David W. Caress Fri 8:00 Hall A-C T51B-2566 (poster)
Volcanology of the Alarcon Rise, Gulf of California
Ryan A. Portner Fri 8:00 Hall A-C T51B-2569 (poster)
Rhyolite, dacite, andesite, basaltic andesite, and basalt volcanism on the Alarcon Rise spreading-center
Brian M. Dreyer Fri 8:00 Hall A-C T51B-2570 (poster)
Effect of melt composition and crystal content on flow morphology along the Alarcón Rise, Mexico
Julie F. Martin Fri 8:00 Hall A-C T51B-2571 (poster)
Newly discovered hydrothermal system on the Alarcón Rise, Mexico
Jennifer B. Paduan Fri 8:00 Hall A-C T51B-2572 (poster)


How methane hydrates effect the shape and stability of the seafloor

For over 20 years MBARI geologist Charles Paull has studied sites around the world where methane hydrate (an ice-like mixture of methane and water) lies buried within seafloor sediments or has turned into a gas and bubbled out into the overlying seawater. Recently Paull’s work on the distribution and stability of methane hydrates has taken on new urgency, due to the possible effects of hydrates on seafloor stability and on global climate change. In two AGU presentations, Paull will describe his recent discoveries in the Canadian Arctic and summarize the tell-tale signs of methane venting that he has observed around the world, some of which have baffled marine geologists for decades.

Distinctive geomorphology of gas venting and near seafloor gas hydrate-bearing sites
Charles Paull Thu 8:00 3024 OS41E-01 (talk)
Active seafloor gas vents on the shelf and upper slope in Canadian Beaufort Sea
Charles Paull Thu 17:15 3024 OS44A-06 (talk)

lrauv_control3-200Undersea robots use artificial intelligence to track and map oceanic fronts and algal blooms

In June 2012, MBARI engineers programmed a newly developed autonomous underwater vehicle (AUV) to find and track an “upwelling front” (the landward edge of a plume of cold, nutrient-rich water) flowing across Monterey Bay. As the front moved and changed shape over time, the AUV moved with the front, automatically navigating a zigzag course to create an extremely detailed three-dimensional picture of the front over a four-day period. Upwelling fronts are biological hot spots, were marine organisms, from microscopic algae to blue whales, congregate in large numbers. Thus, understanding how these features evolve can provide new insights into everything from fisheries biology to harmful algal blooms. MBARI AUVs have also been programmed to automatically find, follow, and map algal blooms as they drift through coastal waters, even when these blooms are not visible at the sea surface. These achievements will be described in the AGU talk and poster listed below:

Observing coastal upwelling front dynamics by AUV tracking, remote sensing, and mooring measurements
Yanwu Zhang Wed 8:45 3011 OS31H-04 (talk)
Localization and tracking of submerged phytoplankton bloom patches by an autonomous underwater vehicle
Michael A. Godin Thu 13:40 Hall A-C OS43E-1869 (poster)

Chemical sensors on automated profiling floats provide detailed views of oxygen minimum zones

Oxygen minimum zones are naturally occurring layers within the ocean where oxygen concentrations are so low that many fish and other large animals cannot survive. For decades, oceanographers have known that these layers form where organic debris sinks down from the surface and is decomposed by marine bacteria, which also consume oxygen. Recent research has suggested that oxygen minimum zones have become thicker and more intense in the last few decades. However, the details of this process are not well understood.

To study oxygen minimum zones in greater detail, MBARI chemist Ken Johnson equipped three “Apex” automated profiling floats with chemical sensors that continuously measure concentrations of oxygen, nitrogen (an important nutrient for bacteria), and tiny particles in seawater. After being released from a ship, these floats periodically rise and sink, creating profiles of changes in the oxygen minimum zone over time. As Johnson describes in his AGU poster, data from these instruments showed that algal blooms near the surface sent pulses of sinking debris into deeper water, resulting in increases in the consumption of nitrate within the oxygen minimum zone. At the same time, the number of tiny particles in the oxygen minimum zone increased-perhaps a sign that large populations of bacteria were consuming the nitrate. This preliminary data shows that oxygen minimum zones are far more dynamic and changeable than previously believed.

Observing the nitrogen cycle in the Arabian Sea and Eastern Tropical North Pacific with chemical sensors on profiling floats
Kenneth S. Johnson Thu 13:40 Hall A-C B43C-0418 (poster)

foce-center-cc2-200Ocean-acidification monitoring system collects longest continuous record of high-precision pH changes in the deep sea

During 2011 and 2012, MBARI researchers conducted several experiments using the deep Free-Ocean Carbon Experiment (dpFOCE), the world’s only experiment to test the affects of ocean acidification on deep-sea animals in their native habitat. Over a 15-month period, custom-designed pH meters on the dpFOCE system measured minute-by-minute changes in the acidity of the surrounding seawater to within about 0.001 pH units. The data showed subtle and unexpected changes in seawater pH caused by tides, internal waves, and coastal upwelling. These findings will be described in an AGU poster by MBARI marine chemist Ed Peltzer.

Long-term, high frequency, high precision pH measurements on the MBARI deep-water FOCE Experiment at the MARS cabled observatory in Monterey Bay
Edward T. Peltzer Fri 13:40 Hall A-C OS53C-1989 (poster)

For additional information or images relating to this article, please contact: Kim Fulton-Bennett