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Abbreviation for harmful algal blooms, also known as marine phytoplankton blooms or red tides. In this naturally occurring phenomenon for which instances are reported for around 300 species blooms with cell concentrations of several million per liter occur. About a fourth of the species produce toxins which cause damage or kill other flora and fauna in the area of the bloom.

HAB Program
An IOC program originating with the formation of an Ad hoc Intergovernmental Panel on Harmful Algal Blooms (IPHAB) in 1991. The panel was requested to identify adequate resources for a sufficiently broad program to solve some of the problems caused by algal blooms. The first session of IPHAB was held in 1992 and the HAB Program plan was adopted in 1993. See the HAB Program Web site.

More later.

Hadley Cell
A part of the atmospheric circulation system extending from the Equator to 30$ ^\circ$ latitude on both sides of the Equator. It is a thermally-driven system in which heated air rises at the Equator, flows poleward, cools and descends at subtropical latitudes, and then flows back towards the Equator. This description was suggested by Hadley in the 18th century.

hadopelagic zone
One of five vertical ecological zones into which the deep sea is sometimes divided. The is the lowest of the levels and is separated from the overlying abyssopelagic zone at about 6000 meters. See Bruun (1957).

Haida Current
A narrow, poleward flowing surface current over the continental slope of northwestern British Columbia and southwestern Alaska. It is seasonal, occuring predominantly between October and April with maximal flow taking place in midwinter from November through February. Its characteristics include a minimal length of 200-300 km, a width of 20-30 km, a depth scale of 500 m, a near-surface speed typically around 0.1 m s$ ^{-1}$, and a near-surface temperature signature about 1$ ^\circ$ C greater than ambient. The temporal variability is not well known, although it evinces spatial variability in the form of large-amplitude (around 10 km) mesoscale waves and eddies. The primary driving mechanisms are wind stress and alongshore sea surface slope. See Thomson and Emery (1986).

Related to salinity.

Halmahera Sea
A regional sea located in the central eastern part of the Australasian Mediterranean Sea. It is centered at about 1$ ^\circ$ S and 129$ ^\circ$ E and is bordered by the Pacific Ocean to the north, Halmahera to the west, Waigeo and Irian Jaya to the east, and the Seram Sea to the south. It covers about 95,000 km$ ^2$ and the topography comprises a number of separate basins and ridges, the chief of which is the Halmahera Basin reaching a depth of 2039 m. Other prominent geographic features include Kau Bay (between the two northward pointing lobes of Halmahera), Buli Bay (between the two eastward pointing lobes), Weda Bay (between the two southward point lobes), the Jailolo, Bougainville and Dampier Straits connecting it to the Pacific, and the Obi Strait connecting it to the Molucca Sea.

The surface salinities range from 34 (March through May) to 34.6 (September through November) and the temperatures from 25.7$ ^\circ$ C in August to 28.6$ ^\circ$ in May. The surface currents are variable with the seasonal monsoon winds. The deep water in the Halmahera Basin is renewed by water from the Pacific which passes from north to south over sills 700 m and 940 m deep. The surface waters are a mixture of oxygen rich Pacific water and oxygen poor water from the Seram Sea. See Fairbridge (1966) and Cresswell and Luick (2001a).

In oceanography, a relatively sharp change in salinity with depth.

halocline catastrophe
A process wherein deep convection and the formation of bottom waters ceases if the ocean surface salinity decreases sufficiently via enhanced freshwater input. This process is thought to have shut down the thermohaline overturning cell in the Atlantic in the past. See Bryan (1986).

Acronym for Hamburg Model of the Ocean Carbon Cycle.

Happel, Eberhard (1647-1690)
A German writer of epics, romance and adventure who published a book entitled Groste Denkwurdigkeiten der Welt oder Sogenannte Relationes Curiosae in 1985 which contained the second chart ever to depict the global ocean circulation. His chart and explanations were very similar to those of Kircher's previous and first-published chart. He also favored the explanation for the tides that had water being withdrawn from the oceans through the north pole and expelled from the south pole, although differing slightly from Kircher on the matter of timing. Happel had the water being withdrawn and discharged at special hours rather than just being rhythmically passed through the earth. See Peterson et al. (1996).

harbor wave
A type of seiche found in harbors. The Japanese word ``tsunami'' means ``harbor wave'' but is a misnomer for what is really a seismic sea wave, more popularly (and even more incorrectly) known as a tidal wave.

A frequency that is a simple multiple of a fundamental frequency. A second harmonic, for example, would have twice the frequency of the fundamental.

Haro Strait Experiment
See the Haro Strait Experiment Web site.

Harrison, John (1693-1776)
See Peterson et al. (1996), p. 53.

Bernard Haurwitz (1905-1986)
An atmospheric scientists who published many basic contributions to the study of short-period atmospheric wave motions, planetary waves (including atmospheric tides), and vortex motions in tropical cyclones. He also published on atmospheric radiation, the wave structure of noctilucent clouds, and internal tides in the oceans.


Hawaii-Tahiti Shuttle Experiment
See Wyrtki et al. (1981).

Heard Island Feasibility Test (HIFT)
An ocean acoustical tomography experiment in which computed geodesics (minimum paths) for acoustics transmissions were compared with observations. The acoustic source was suspended from the R/V Cory Chouest 50 km southeast of Heard Island located about halfway between Africa and Australia at about 50$ ^\circ$ S in the South Indian Ocean. Receiver arrays were located on various research vessels throught the oceans as well as at South Africa, Bermuda, India, Christmas Island, Samoa, Hobart (Tasmania) and Monterey (California). See Baggeroer and Munk (1992) and Munk et al. (1995).

heat capacity
The heat capacity of a body is the product of its mass and its specific heat.

heat equator
See thermal equator.

Acronym for High Energy Benthic Boundary Layer Experiment. See Nowell et al. (1982) and Nowell and Hollister (1985).

An isotope of helium that is useful in ocean tracer studies. There are two sources for Helium-3 in the ocean: volcanic sources at mid-ocean ridge crests and the decay of man-made tritium. The former source makes helium-3 a unique tracer due to its being injected into the middle of the water column. This leads, for example, to a stark contrast in helium-3 content between incoming and outgoing deep waters in the Pacific. It also provides a dramatic picture of the relative movement of helium poor NADW and helium rich (due to sources in the Pacific) ACC water. The helium-3 tritium decay (sometimes called trituigenic) source is much larger than the deep sea sources, with the global average of the latter being about 4 at/cm2/s as opposed to a northern hemisphere average of about 32 at/cm2/s for the former.

Helium-3 is used in combination with tritium to date water on timescales of 0-10 years with a resolution of around 0.1 years (in North Atlantic surface waters). It is better to treat them as separate but related tracers on longer timescales or in the presence of extensive mixing. Their relationship is a diagnostic of vertical versus horizontal mixing, and has been used to assess an upper limit to vertical mixing that is consistent with physical estimates. This has also been used to show that horizontal mixing is the dominant mechanism of thermocline ventilation in subtropical gyres. See Sarmiento (1988) and Broecker and Peng (1982).

Helland-Hansen, Bjorn
More later.

Or or pertaining to continental margins and the adjacent abyssal plains.

To be completed.

Acronym for Humidity Exchange Over the Sea, a 1986 program to measure water vapor and droplet fluxes from sea to air at moderate to high wind speeds. HEXOS was the first comprehensive open ocean air-sea flux field project to emphasize surface exchange processes. It was conducted on the Dutch Noordwijk platform, and featured the largest range of windspeeds over which momentum, sensible heat, and latent heat fluxes had been measured. It provided the physical basis for linking aerosol, sea spray, and sensible and latent heat fluxes under a common framework. See Katsaros et al. (1987), Geernaert (1990), Smith et al. (1992) and DeCosmo et al. (1996).

Acronym for High Intake, Defined Excitation Bathyphotometer, a vertical profiler for measuring stimulated bioluminescence. The features include statistically rigorous sampling (faciliatated by high pumping rates), hydrodynamically calibrated excitation at the entrance to the large volume detection chamber, and the capability of rapid vertical deployment to depths of 500 m at descent velocities up to 50 m min$ ^{-1}$. See Widder et al. (1993).

Acronym for Heard Island Feasibility Test.

Abbreviated form for high pressure center.

high pressure center
In meteorology, a region of relatively high barometric pressure. These are characterized by subsidence at altitude and by divergence near the surface. They predominate at 30 and 90$ ^\circ$ latitude where the global generation circulation patterns exhibit downward motion. This type of circulation feature is also known as an anticyclone and as such rotates clockwise/counterclockwise in the norther/southern hemisphere. High pressure systems are generally characterized by clear skies and fair weather since cloud development is impeded therein, and winds are also generally light.

High Resolution Profiler (HRP)
An oceanographic instrument designed to collect fine- and microstructure data during vertical profiles. As the HRP is lowered has two profiling modes, with the transition between the fine and micro modes triggered by the onboard CTD pressure sensor reaching a user-defined threshold value. The fine structure sensors are sampled at 10 Hz and the microstructure sensors at 200 Hz, with the fine sampling continuing simultaneously with the micro sampling. The HRP is designed to minimize ship-induced noise in the measurements, and as such profiles while falling freely from the ship until it releases a set of weights and ascends to the surface to be recovered. The nominal descent rate is 0.6 ms$ ^{-1}$ with a 1000 meter dive typically taking thirty minutes during which half a megabyte of fine data and two megabytes of micro data will be acquired and stored. The data is downloaded from instrument memory to a shipboard computer once it has been loaded on deck. See Schmitt et al. (1988).

HiHo HiHo Experiment
Acronym for Harmonious Ice and Hydrographic Observations - Heat In, Halide Out Experiment, a Antarctic CRC experiment to study the Antarctic pack ice during winter. The project aims include: (1) providing a quantitative assessment of the mass budget and Antarctic winter sea ice and to relate this to the rate of water mass modification; (2) providing a quantitative estimate of the surface energy exchanges in the winter Antarctic sea ice zone and, in conjunction with FORMEX, to relate surface vertical energy exchange to the ocean heat budget and advection; and (3) describing the processes by which new ice deforms and thickens and the atmospheric and ocean forcing which determine these processes. See the HiHo Web site.

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Manbreaker Crag 2001-08-17