NOAA is the primary federal agency responsible for understanding
and predicting climate changes, and their impact on Earth environments
and resources. As stated in the NOAA Strategic Plan for 2003-2008,
this includes "understanding of past climate variations and
atmospheric, oceanic, and land-surface processes that influence
climate." The oceans are by far the largest repository of carbon
on the planet, and play a crucial role in the atmospheric inventory
of greenhouse gases, in particular carbon dioxide and methane. Most
of the global carbon is sequestered in deep sea sediments. However,
seafloor seeps and vents also contribute both heat and carbon to
the oceans and atmosphere. They are also "hot spots" for
biodiversity and life in the ocean. Listed below are examples of
NURP seep and vent research that has changed fundamental understanding
of life on earth and the impacts the oceans have on global climate:
Management Objective - Understanding Past Climate Variations
Most of the past 14,000 years is offshore from current sea level.
Analyses of ancient shorelines and the modern processes that affect
the geologic record in rocks, ancient reefs, and shells (taphonomy)
provide a basis for understanding current and predicting future
climate changes.
Ancient
Shorelines - Global temperature rise since the last glacial
stage 14,000 years ago has been as rapid as any time in recorded
history. Over the past 1.5 million years there have been many
rapid transitions from glacial to interglacial stages. All this
history is accessible on the continental shelf. Along the Gulf
of Mexico and southeast coast, carbonate ledges outcrop all across
the shelf. These formed during various low-sea level stands. The
first step was to date the ancient shoreline rocks. Most of the
surficial rocks are recent limestone formed by attached animals
such as corals and coralline algae. Reaching the original rock
base requires diver-operated cores. By using divers, core sites
can be precisely located in the target features, e.g., more vertical
surfaces with less biotic cover, something that could not be done
by lowering corers from a surface vessel. Based on these analyses,
researchers reconstructed the approximate speed of past sea level
changes and environmental conditions such as temperature at the
time of formation.
Management Objective - Describe Ocean Processes that Influence
Climate & the Carbon Cycle
Seafloor vents and seeps are significant sources of heat and materials
to the oceans. Undersea technologies are required to explore, visit,
and measure the rates and impacts of emissions from these features,
which range in size from a bubble streams to undersea volcanoes.
Gas
Hydrate Outcrops in the Gulf of Mexico - Only in the 1990s
have scientists begun to realize the extent of gas hydrates beneath
the sea. Gas hydrates are ice crystal cages that form around a
molecule of natural gas, mostly methane, the most potent greenhouse
gas in the atmosphere and second only in concentration to carbon
dioxide. One cubic foot of hydrate ice holds 160 cubic feet of
natural gas! Hold a match to it, and the ice will burn away. Current
estimates indicate that there is ten times more carbon in gas
hydrates then all other fossil fuels in the world combined. They
occur off every shoreline from the tropics to the poles. Thus,
oil and gas companies around the world are now exploring the possibility
of mining gas from the ice. The disadvantage however is that,
due to the volatile nature of the reservoir, mining is hazardous.
Oil companies try to steer around known beds with pipelines and
platforms for fear that the bottom will melt away from under their
structures. In the early 1990s NURP dives discovered gas hydrate
beds outcropping at the seafloor in the northern Gulf of Mexico.
More recently, studies suggest that massive meltdowns of seafloor
hydrates may have caused regional to global climate change, e.g.,
5°C rise over a 1000 years. Since
these discoveries, the outcrops have served as natural laboratories
to better understand their stability and surrounding conditions.
Custom equipment has measured the rate of dissociation in relation
to minor changes (1°C) in bottom water temperature. In 1997,
scientists discovered a news species of iceworm living in hydrates,
likely grazing off other microbial life that appears to thrive
in this extreme environment.
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