Global Climate and Sea-Change Models Require Extremely Precise Measurements
SeaKeeper 1000™ Data Provides Necessary Accuracy

by John Englander

The most basic mechanisms of oceanography deal with the movement of portions of the ocean. This is very similar to the way we look at air masses when we want to understand weather. We have all heard meteorologists say things like, “a mass of warm moist air is coming in from the west that will give us a period of rainy weather.” Meteorologists track these air masses principally by measuring temperature and barometric pressure. While water in the oceans appears to be quite different from air, there are similarities.

SeaKeepers technicians validate sensor data in the new
SeaKeepers calibration laboratory in Fort Lauderdale.

Surprisingly the oceans have definable masses and “fronts” that resemble those in the atmosphere. Just like weather they are essentially pressure fronts, and the movement and mixing of sea water happens in three dimensional spaces, just as in the atmosphere. The atmosphere extends up from the earth’s surface to about 60,000 feet – about 11 miles, whereas the oceans range in depth to a maximum of 35,000 feet, but average about 12,000 feet globally—just over two miles.

The image shows the tracks of the satellite data transmissions for SeaKeepers vessels in 2008. In many cases overlapping tracks hide multiple transmission points. In 2008 SeaKeepers will take approximately 9 million data samples; each data sample typically represents at least 10 different precise measurements, which are available to thousands of scientists worldwide analyzing and modeling our changing oceans.

One fundamental difference is that water is nearly non-compressible. So pressure in the ocean is not defined by density as in the atmosphere. Rather pressure is generally the indicator of depth.

Just as atmospheric fronts are driven primarily by temperature and barometric pressure, ocean fronts are driven by differentials of temperature and salinity. Additionally, both the atmosphere and ocean have another huge force, the Coriolis Effect, which comes from the spinning of the earth itself.

SeaKeepers measures a number of ocean and atmospheric parameters that are important to scientists trying to understand and model the oceans. While in operation, our SeaKeeper 1000™ systems simultaneously measure air temperature and barometric pressure, plus sea surface temperature and salinity, every minute.

A sample of transmitted raw data collected from Carnival Triumph, with preliminary QA/QC applied.
Click on image for a more readable view.

For example, in just one day, at 13 knots, a SeaKeeper-equipped vessel provides scientists with 1,440 samples covering 312  nautical miles. If only 20 SeaKeepers vessels were underway on a given day, they would take nine million data samples in a year. Assuming an average speed of 13 knots, that would mean transects covering well over two million miles of ocean.

Satellites provide very fast and comprehensive measurements about the Earth, including sea surface temperature. Yet due to a number of changing environmental factors, including water vapor, dust and cloud cover, they cannot achieve anything approaching the two-decimal-place accuracy of the SeaKeeper 1000™ monitoring system, and have essentially no capability
for fine-scale salinity measurements.

Salinity measurements can range from zero in fresh water to 330 parts per million (ppm) in rare spots like the Dead Sea, but generally open-ocean salinity ranges from 34 to 38 ppm. [Click here to learn more about the SK1000 Measurements.] It is this tiny variation that helps scientists to understand and predict the forces and movement of the ocean. These data have short-term applications in terms of marine weather forecasts, but longer term they show patterns of changes in ocean currents. When people speculate about cataclysmic changes to the oceans and our climate, they quickly look to such things as changes to major ocean currents.

Speculation about the possible change or shut down of the Gulf Stream (such as in the highly exaggerated sci-fi movie “The Day After Tomorrow”) is based upon a real scientific concern that changing temperature and salinity differentials could portend massive changes to the primary ocean currents.

The way to monitor and model these systems is by taking many highly accurate readings of temperatures and salinities over time. Last year SeaKeepers took nine million data samples across the surface of the seas — spanning an estimated 2.4 million miles. Considering our total operating budget is slightly over a million dollars this is an amazing level of efficiency— something like ten cents for a set of measurements, all costs included. Note that each measurement set includes at least 10 separate parameters.

Where the SeaKeepers system tracks parameters across hundreds of miles of ocean daily, other observing systems do vertical series of measurements—so called profilers. These devices go up and down in a pattern from the surface to a depth of two kilometers. Combined, these two kinds of measurements provide scientists with a better picture of the ocean's driving forces.

1 ppm and a temperature difference of 1 degree would be worth noting. A few miles down, it would be important to resolve salinity and temperature down to .001.

SeaKeepers’ systems are an increasingly important part of understanding the ocean. Setting up weather and climate stations on land is easy. The seas, however, have very few weather and climate monitoring stations. With 55 installed systems and 20 more in process, SeaKeepers is already a significant provider of critical ocean measurements. The fact that SeaKeeper 1000™ units take measurements every minute has proven a tremendous innovation and a real source of value to the scientific community.

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