Sea Technology

NOV 2017

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Page 39 of 53

38 st / November 2017 Sea Level Fingerprints Indicate Climate Changes Researchers have reported the first observation of sea level "finger- prints," tell-tale differences in sea level rise around the world in response to changes in continental water and ice sheet mass, the American Geophysical Union reported. Scientists have a solid understand- ing of the physics of sea level finger- prints but have never had a direct de- tection of the phenomenon until now. As ice sheets and glaciers undergo climate-related melting, they alter Earth's gravity field, which causes non- uniform sea level change. The team calculated sea level fin- gerprints using time-variable gravity data collected by the twin satellites of NASA's Gravity Recovery & Climate Experiment between April 2002 and October 2014. During that time, the global mean sea level grew by about 1.8 mm per year, with 43 percent of the increased water mass coming from Greenland, 16 percent from Antarctica and 30 percent from mountain gla- ciers. The scientists verified their cal- culations of sea level fingerprints as- sociated with these mass variations via ocean-bottom pressure readings from stations in the tropics. With improved understanding through GRACE data and other tech- niques, scientists can now take any point on the global ocean and deter- mine how much the sea level there will rise as a result of glacier ice melt. ALAMO Tracks Irma Effects For Better Hurricane Prediction As Hurricane Irma approached U.S. shores in September, researchers sponsored by the U.S. Office of Na- val Research (ONR) used air-dropped autonomous sensors to compile real- time ocean observations to help fore- casters predict the strength of future tropical storms. This marks the first time the sensors—called ALAMO (Air-Launched Autonomous Micro Observer) sensors—were used in hur- ricane prediction research. While stan- dard computerized prediction models rely on atmospheric data like air tem- perature, humidity, altitude and wind speed and direction, the ALAMO sen- sors measure oceanographic phenom- ena beneath the sea surface. Hurricane Irma is one of the strongest storms ever recorded in the Atlantic Ocean. Such storms are notoriously difficult to pre- dict, presenting a volatile meteorologi- cal cocktail that can change direction, speed and strength quickly and unex- pectedly. The sensor data will be used to improve the Navy's Coupled Ocean/ Atmosphere Mesoscale Prediction Sys- tem-Tropical Cyclone—COAMPS-TC, which uses complex algorithms to pre- dict hurricane intensity by processing real-time and historical meteorological data, fed by information from satellites. Buoys with Acoustic Recorders Support German Offshore Wind A species of porpoise endemic to the German coast is very sensitive to sound waves. In order to avoid disturb- ing its natural habitat, German legisla- tion imposes a maximum sound level that must not be exceeded, especially by offshore wind farms. Since 2014, RTsys has been pro- viding buoys equipped with acoustic recorders, which analyze data in real time. These buoys are based on under- water acoustic recommendations and standards. RTsys is now recognized and authorized by German authorities. Offshore wind farm personnel can use these buoys to manage construction work, enabling them to make quick and reliable decisions. ONC WERA Radar Shows Value As Early-Warning System Installation of Ocean Networks Canada's (ONC) WERA high-frequen- cy oceanographic radar near Tofino on the west coast of Vancouver Island was completed March 2015 by ASL Envi- ronmental Sciences Inc. of Victoria, British Columbia; Northern Radar Inc. of St. John's, Newfoundland; and Hel- zel Messtechnik GmbH of Germany. The primary goals of the radar, which provides oceanographic data and tsu- nami monitoring in near real time under all weather conditions, are to detect tsunamis generated off the west coast of Vancouver Island and, in the future, provide valuable warning time. On October 14, 2016 at 05:45 UTC the ocean radar system sent out a tsunami alert after it detected and identified the distinctive signatures of a changing surface velocity potentially associated with a tsunami. There was, however, no seismic activity at that time to trigger an earthquake-generat- ed tsunami. Although there was no tectonic ac- tivity, the system did record an event with an unusual wave propagation cur- rent that coincided with the passage of an atmospheric cold front. Weather conditions around October 14 were characterized by strong winds and a stormy sea state caused by the rem- nants of Typhoon Songda 2016, a trop- ical disturbance formed west–south- west of Hawaii that crossed the Pacific Ocean and struck the Pacific North- west region of the U.S. and Canada as a powerful extratropical cyclone. The abrupt changes in atmospheric pres- sure generated a meteorological tsu- nami. Analysis of data from the tide gauge in Tofino showed a sea level distur- bance with a maximum height of 80 cm nearshore. The radar was able to detect signatures of the event 20 min- utes before the waves reached Bam- field and 1 hour in advance for Tofino. The radar data from the British Co- lumbia coast demonstrates the high sensitivity, reliability and potential of WERA for hazardous event detection and its value for early-warning systems. Network of Monitoring Buoys For Kiel Canal Project OSIL has supplied a network of seven 1.9-m data buoys to DHI in Denmark in support of a long-term monitoring project in Kiel, Germany. The sturdy buoy systems each incorpo- rate two Sea-Bird Scientific WET Labs multiparameter water quality sensors; one mounted at the surface within the robust central buoy structure to pre- vent damage to the instrument and the other on a mooring frame that is suspended 2 m above the seabed and accommodates a Nortek AWAC on a gimbal to monitor currents and waves. The exclusive mooring design includes a data swivel to ensure that the sub- sea instruments can continually report data without the risk of cable entangle- ments in the dynamic environment. The buoys have a substantial power consumption rate owing to the high sampling frequency and real-time data transmitted almost continuously, as re- quired by the client. ST environmental monitoring

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