96
of the future for coastal ocean research. Already, satellite sensors such as the Coastal
Zone Color Scanner had produced spectacular images of ocean phytoplankton
blooms. I believed they could also inform the sediment dynamics near rivers. My
advisor, Dr. Chuck Nittrouer, thought I was nuts. He logically explained that visible
light only penetrates the uppermost layer of the ocean, and most sediment moves
near the seafloor. He was right. Nevertheless, I was certain that remotely sensed
imagery could be used to inform what is happening at the ocean surface, and this
would indicate what transpires on the ocean floor below – at least sometimes. I was
right too. In fact, most people don’t know that most of our maps of bathymetry
(ocean depths) are based on satellite measurements of the sea surface elevation (not
the seabed). Altimetry measurements are used to calculate the depth of the seafloor
and corrected using local measurements where available. From the combination of
space and ship-based data, our global maps of the seafloor are still derived today. Of
course, we have much better knowledge of the depths in well-trafficked coastal
zones, especially near ports. But many don’t realize that only 18% of the ocean floor
has been mapped at a resolution of 1 km or less – more on that later. The point I
want to make here is that remote sensing now provides tremendous information
about our coasts and oceans. An arsenal of satellites using a variety of techniques
(not simply visible light) measure the dynamic earth and its coastal and ocean phenomena. We still have many limitations in our sensing abilities temporally and spatially due to resolution, cloud cover and other factors, but our ability to study the
global coast has greatly improved.
One of my favorite images of coast was captured following a storm in February
2010 (Fig. 6.2). This MODIS (Moderate Resolution Imaging Spectroradiometer)
image reveals how the shallow waters of the Albemarle and Pamlico sounds in
northern North Carolina were stirred up by the wind-generated waves and currents
during the storm. The dark-colored water, filled with sediment and dissolved materials from land, is being carried out of the inlets at the eastern side of this large
estuarine system. Once on the NC shelf, the sediment-laden water is entrained in
nearshore currents moving along the coast and eventually by the Gulf Stream into
the open Atlantic. Images like these highlight the potentially rapid connection
between land and sea, a research topic we continue to learn more about. During
storms, we know the estuarine seafloor is being agitated because we can see it in
satellite imagery, have measured the conditions (Fig. 6.2, Top) and have experienced the power of storms first-hand. My colleague, Dr. Reide Corbett, and I along
with several former students and collaborators, deployed instrumented tripods in
these areas. There are many stories from our times in the field. One of the most
memorable was when a strong thunderstorm descended upon on our team as we
worked at the “Albemarle Sound Site”, located in the middle of the vast body of
water. We affectionately referred to this location by its acronym (the ASS), because
things had a propensity for going wrong. On this day, an ominous storm system
descended upon on us (Fig. 6.3). Lightening was shooting like fireworks in all directions as the storm approached, and we were very exposed -- on a small boat tied
up to a metal piling with nowhere to find shelter. Without time to finish our work or
J. P. Walsh
of the future for coastal ocean research. Already, satellite sensors such as the Coastal
Zone Color Scanner had produced spectacular images of ocean phytoplankton
blooms. I believed they could also inform the sediment dynamics near rivers. My
advisor, Dr. Chuck Nittrouer, thought I was nuts. He logically explained that visible
light only penetrates the uppermost layer of the ocean, and most sediment moves
near the seafloor. He was right. Nevertheless, I was certain that remotely sensed
imagery could be used to inform what is happening at the ocean surface, and this
would indicate what transpires on the ocean floor below – at least sometimes. I was
right too. In fact, most people don’t know that most of our maps of bathymetry
(ocean depths) are based on satellite measurements of the sea surface elevation (not
the seabed). Altimetry measurements are used to calculate the depth of the seafloor
and corrected using local measurements where available. From the combination of
space and ship-based data, our global maps of the seafloor are still derived today. Of
course, we have much better knowledge of the depths in well-trafficked coastal
zones, especially near ports. But many don’t realize that only 18% of the ocean floor
has been mapped at a resolution of 1 km or less – more on that later. The point I
want to make here is that remote sensing now provides tremendous information
about our coasts and oceans. An arsenal of satellites using a variety of techniques
(not simply visible light) measure the dynamic earth and its coastal and ocean phenomena. We still have many limitations in our sensing abilities temporally and spatially due to resolution, cloud cover and other factors, but our ability to study the
global coast has greatly improved.
One of my favorite images of coast was captured following a storm in February
2010 (Fig. 6.2). This MODIS (Moderate Resolution Imaging Spectroradiometer)
image reveals how the shallow waters of the Albemarle and Pamlico sounds in
northern North Carolina were stirred up by the wind-generated waves and currents
during the storm. The dark-colored water, filled with sediment and dissolved materials from land, is being carried out of the inlets at the eastern side of this large
estuarine system. Once on the NC shelf, the sediment-laden water is entrained in
nearshore currents moving along the coast and eventually by the Gulf Stream into
the open Atlantic. Images like these highlight the potentially rapid connection
between land and sea, a research topic we continue to learn more about. During
storms, we know the estuarine seafloor is being agitated because we can see it in
satellite imagery, have measured the conditions (Fig. 6.2, Top) and have experienced the power of storms first-hand. My colleague, Dr. Reide Corbett, and I along
with several former students and collaborators, deployed instrumented tripods in
these areas. There are many stories from our times in the field. One of the most
memorable was when a strong thunderstorm descended upon on our team as we
worked at the “Albemarle Sound Site”, located in the middle of the vast body of
water. We affectionately referred to this location by its acronym (the ASS), because
things had a propensity for going wrong. On this day, an ominous storm system
descended upon on us (Fig. 6.3). Lightening was shooting like fireworks in all directions as the storm approached, and we were very exposed -- on a small boat tied
up to a metal piling with nowhere to find shelter. Without time to finish our work or
J. P. Walsh