Weekly Ocean News

WEEKLY OCEAN NEWS

DATASTREME OCEAN WEEK SIX: 2-6 March 2015

For Your Information

Biomixing in ocean motion -- If you would like information on recent findings that indicate marine organisms contribute to motion in the ocean, please read this week's Supplemental Information…In Greater Depth.

Ocean in the News

Eye on the tropics --- As meteorological summer in the Southern Hemisphere (December, January and February) ended over the past weekend, tropical cyclone activity was limited to the southern Indian Ocean basin. Tropical Storm Glenda formed early last week from a low pressure area approximately 600 miles to the south of Diego Garcia. This tropical storm traveled initially to the southwest during the week and then to the south before curving to the south-southeast. By late last week, wind shear was stretching Glenda as it was located approximately 650 miles to the east-southeast of Port Louis, Mauritius. Glenda was expected to lose its tropical characteristics and become a midlatitude storm. The NASA Hurricane Page has additional information and satellite images for Tropical Storm Glenda.
Ice covered lakes and bays across Northeast seen from space -- A portfolio of recent natural color satellite images focuses on the widespread ice cover on the waters of the eastern Great Lakes and the various bays and harbors along the Middle Atlantic and New England coasts, which developed because of the exceptionally cold month of February 2015. The images were made from the the Operational Land Imager (OLI) on NASA's Landsat 8 and the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite. [NASA Earth Observatory]
Recent two-year spike in sea level found along the Atlantic coast -- Scientists from the University of Arizona and NOAA have discovered an approximately four inch jump in the sea level of the western North Atlantic Ocean from New York to Newfoundland between 2009 and 2010 because of changes in the Atlantic Meridional Overturning Circulation and also a change in part of the North Atlantic Oscillation. The spike in sea level was discovered from analysis of monthly tide-gauge records collected by 40 tide gauges along the Atlantic coast since the early 20th century. The team used computer climate models From NOAA's Geophysical Fluid Dynamics Laboratory to project a higher frequency in such spikes in the future, which would be made worse by rising sea levels due to ocean warming and melting land ice. [NOAA Oceanic and Atmospheric Research News]
First global rainfall and snowfall map from new satellite is released -- During the last week NASA released the first global map of rainfall and snowfall obtained from data collected by the agency's new Global Precipitation Measurement (GPM) Core Observatory on the first anniversary of the spacecraft's launch. This first global rainfall and snowfall map from the GPM Core Observatory along with 12 other satellites is a nearly two-minute video covering approximately 87 percent of the Earth's surface area over a time span running from April to September 2014 using an update-interval of every half hour. This video was produced by NASA's Integrated Multi-satellite Retrievals for GPM (IMERG) that assembled the data from GPM and the additional NASA, NOAA and Defense Department satellites from the US and those from Japan, India, France and EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites). [NASA Goddard Space Flight Center News]
A "false pause" in global warming attribute to interactions of ocean oscillations -- Researchers from Penn State University claim that the recent "false pause" or slowdown in climate warming appears to be due in part to the natural oscillations in the climate system, with some of these rhythmic variations being driven by substantial natural, internal climate variability in the North Atlantic and North Pacific oceans that are on time scales of decades. The Atlantic Multi-Decadal Oscillation (AMO) tends to oscillate with a periodicity of between 50 and 70 years, while the Pacific Decadal Oscillation (PDO) varies over a broader range of time scales [Penn State University News]
Exploring the differences in the global temperature records -- NASA's Earth Observatory describes the reasons why differences arise in the time series of global temperatures produced by NOAA's National Climatic Data Center, NASA's Goddard Institute for Space Studies, the United Kingdom's Met Office Hadley Center/Climatic Research Unit and the Japanese Meteorological Agency. Although the long term trends in these four time series are generally close over the last 134 years, the subtle differences appear magnified when comparisons are made of the rankings of highest yearly global temperatures, especially over the last decade. The differences between the global temperature records of these four institutions arise from how each handles the spatial averaging of temperatures over data sparse areas over the oceans and the polar caps. [NASA Global Climate Change News]
An All-Hazards Monitor -- This Web portal provides the user information from NOAA's National Weather Service, FAA and FEMA on current environmental events that may pose as hazards such as tropical weather, fire weather, marine weather, severe weather, drought and floods. [NOAA/NWS Daily Briefing]
Earthweek -- Diary of the Planet [earthweek.com] Requires Adobe Acrobat Reader.

Concept of the Week: Abyssal Storms

Until recently, ocean scientists thought of the deep ocean abyss as a dark and cold, but serene place where small particles rained gently onto the ocean floor. However, instruments lowered to the sea floor to measure ocean motion or currents and resulting mobilization of bottom sediments detected a much more active environment. Scientists found that bottom currents and abyssal storms occasionally scour the ocean bottom, generating moving clouds of suspended sediment. A surface current of 5 knots (250 cm/sec) is considered relatively strong. A bottom current of 1 knot (50 cm/sec) is ripping. Although this may be called an abyssal storm, the water motion pales by comparison to wind speeds in atmospheric storms.

Abyssal currents and storms apparently derive their energy from surface ocean currents. Wind-driven surface ocean currents flow about the margins of the ocean basins as gyres centered near 30 degrees latitude. (Refer to Figure 6.6, page 152, in your textbook.) Viewed from above, these subtropical gyres rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. For reasons given in Chapter 6 of your textbook and this week's Supplemental Information, surface currents flow faster, are narrower, and extend to greater depths on the western arm of the gyres. These are known as western boundary currents and include, for example, the Gulf Stream of the North Atlantic basin. Abyssal currents are also most vigorous on the western side of the ocean basins, moving along the base of the continental rise, which is on the order of several kilometers deep.

Abyssal storms may be linked to or may actually be eddies (rings) that occasionally break off from the main current of the Gulf Stream (and other western boundary currents). During an abyssal storm, the eddy or ring may actually reach to the bottom of the ocean where the velocity of a bottom current increases ten-fold to about 1.5 km (1 mi) per hr. While that is an unimpressive wind speed, water is much denser than air so that its erosive and sediment-transport capacity is significant even at 1.5 km per hr. At this higher speed, the suspended sediment load in the bottom current increases by a factor of ten. Abyssal storms scour the sea floor leaving behind long furrows in the sediment. After a few days to a few weeks, the current weakens or the eddy (ring) is reabsorbed into the main surface circulation and the suspended load settles to the ocean floor. In this way, abyssal storms can transport tons of sediment long distances, disrupting the orderly sequence of layers of deep-sea sediments. Scientists must take this disruption into account when interpreting the environmental significance of deep-sea sediment cores.

Concept of the Week: Questions

In the subtropical ocean gyres, boundary currents flow faster on the [(western)(eastern)] side of an ocean basin.
Currents in an abyssal storm erode, transport, and redeposit sediments that have accumulated on the [(continental shelf)(deep ocean bottom)].

Historical Events

3 March 1873...US Army Signal Corps established storm signal service for benefit of seafaring men, at several life-saving stations and constructed telegraph lines as original means of communication. (USCG Historian's Office)
3 March 1960...The submarine USS Sargo returned to Hawaii from an Arctic cruise of 11,000 miles, of which 6,003 miles were under the polar ice, reaching the North Pole on 9 February. This cruise marked the first time that a submarine explored the Arctic in winter. (Naval Historical Center)
4-5 March 1899...Tropical Cyclone Mahina (the Bathurst Bay Hurricane) crossed the Great Barrier Reef and generated a 48-ft storm surge across Barrow Point, Queensland, Australia. The Australian pearling fleet was destroyed, over 100 shipwrecks reported and 307 people killed. Barometric pressure fell to an unofficial reading of 915 millibars (27 inches of mercury). (Accord's Weather Calendar) (The Weather Doctor)
5 March 1914...The Spanish ship the Principe de Asturias enroute from Barcelona to Buenos Aires sank with the loss of 445 of the 588 passengers and crew members when it struck the jagged reefs along the Brazilian coast at Ponta Boi in dense fog.
5-6 March 1962...The Great Atlantic Coast Storm of 1962 caused more than $200 million in property damage from Florida to New England. Winds along the Middle Atlantic Coast reached 70 mph raising 40-ft waves, and 42 inches of snow fell at Big Meadows, in the mountains of Virginia--a state record. The storm caused greater alteration of the coastline from Cape Hatteras, NC to Long Island than any previous storm, including hurricanes. A new inlet was cut through Hatteras Island and more than 10 miles of Outer Banks barrier dunes were obliterated. The Virginia shoreline was rearranged by historic tidal flooding caused by the combination of the long stretch of strong onshore winds and the spring tides. A 3-mile long boardwalk in Ocean City, MD was wiped out. (David Ludlum) (Intellicast)
6 March 1521...The Portuguese explorer Ferdinand Magellan reached Guam in his around the world voyage. (Wikipedia)
6 March 1987...The British ferry Herald of Free Enterprise capsized in the English Channel off the coast of Belgium with the loss of 189 people.
7 March 1778...Captain James Cook first sighted the Oregon coast, at Yaquina Bay near present day Newport.
7 March 1932...A severe coastal storm set barometric pressure records from Virginia to New England. Block Island, RI reported a barometric pressure reading of 955.0 millibars (28.20 inches of mercury). (David Ludlum)