Notes from Class Unit 2

Radiation

The transfer of electromagnetic energy, primarily from solar insolation, into the ocean system, driving thermal processes and primary production within the photic zone.

Electromagnetic Spectrum

The full range of all types of electromagnetic radiation, ordered by wavelength or frequency, encompassing visible light, ultraviolet, infrared, and other forms of energy relevant to oceanic processes.

Light Attenuation

The exponential decrease in the intensity of light as it penetrates the water column, primarily due to the combined effects of absorption (conversion to heat or chemical energy) and scattering (redirection by particles and water molecules).

Absorption

The process by which light energy is taken up by water molecules and dissolved or particulate matter in the ocean, converting it into heat or chemical energy (e.g., photosynthesis), leading to a reduction in light intensity and changes in its spectral composition.

Scattering

The redirection of light waves in various directions upon encountering suspended particles (e.g., phytoplankton, detritus) and water molecules within the ocean, reducing light penetration and altering the visual clarity and perceived color of the water.

Isohaline

An isoline on a map or chart that connects points of equal salinity (the concentration of dissolved salts) in a body of water, used to delineate regions of uniform salt content or to visualize salinity gradients.

Sound Navigation and Ranging (Sonar)

An acoustic technology that utilizes the emission and reception of reflected sound waves to detect objects, measure distances (bathymetry), and image the seafloor and subsurface features within marine environments.

Seismic reflection profilers

A geophysical instrument that emits high-energy sound waves into the seabed and records the reflected echoes to generate detailed 2D acoustic images of the subsurface geological layers and structures beneath the seafloor, essential for studying marine geology.

Bathymetry

The measurement and mapping of ocean depths and the topography of the seafloor (its 3D relief), providing essential data for navigation, marine biology, geological hazard assessment, and understanding ocean circulation patterns.

Conservative Constituents

Dissolved substances in seawater whose concentrations and relative proportions remain essentially constant throughout the global ocean, primarily because their oceanic residence times are considerably longer than the ocean's mixing time, making them useful tracers for oceanographic processes (e.g., Chloride, Sodium).

Non-Conservative Constituents

Dissolved substances in seawater whose concentrations are significantly altered by biological, chemical, or physical processes (e.g., uptake by organisms, redox reactions, advection/diffusion) with residence times shorter than ocean mixing, leading to spatially and temporally variable distributions (e.g., nutrients, oxygen).

Adsorption

A surface phenomenon where ions, molecules, or particles adhere to the surface of a solid or liquid (the adsorbent) via physical or chemical forces, without necessarily forming new chemical bonds, playing a role in nutrient cycling and contaminant transport in seawater.

Salinity

A measure of the total amount of dissolved inorganic solids (salts) in seawater, typically expressed in practical salinity units (psu) or parts per thousand (ppt), and influenced by evaporation, precipitation, river runoff, and ice formation/melt.

Nitrogen (N)

An essential macronutrient for marine life, particularly primary producers like phytoplankton, cycling through various inorganic and organic forms in the ocean, including dissolved gaseous nitrogen (\text{N}2), nitrate (\text{NO}3^-), nitrite (\text{NO}2^-), and ammonium (\text{NH}4^+), with its availability often limiting primary production.

Phosphorus (as Phosphate)

A crucial macronutrient for all marine organisms, primarily available as dissolved inorganic phosphate (\text{PO}_4^{3-}) in seawater. It is a key component of DNA, RNA, and ATP, and its concentration is frequently a limiting factor for primary productivity in marine ecosystems, especially in older, deeper waters.

Redfield Ratio

The empirically observed atomic ratio of carbon (C), nitrogen (N), and phosphorus (P) found in marine phytoplankton and across much of the deep ocean, approximately 106 \text{ C} : 16 \text{ N} : 1 \text{ P}, indicating the stoichiometric requirements for primary production and nutrient regeneration in the global ocean.

Saturation Concentration of Gases

The maximum amount of a specific gas (e.g., oxygen, carbon dioxide) that can dissolve in a given volume of water at equilibrium with the atmosphere, which is inversely proportional to temperature and salinity, and directly proportional to the partial pressure of the gas.

Nutrient Residence Times

The average length of time a particular nutrient atom or ion remains in the dissolved phase within a specific oceanic reservoir before being removed by biological uptake, chemical precipitation, or sedimentation, providing insight into the dynamics of nutrient cycling and ecosystem productivity.

Speed of Sound in Seawater

The velocity at which acoustic waves propagate through seawater, typically around 1500 \text{ m/s}, which is significantly faster than in air. This speed is influenced primarily by temperature, salinity, and pressure, with higher values in warmer, higher salinity, and deeper waters.

Major Constituents of Seawater

The six most abundant dissolved inorganic ions that collectively comprise approximately 99\% of the total dissolved solids in seawater: Chloride (\text{Cl}^-), Sodium (\text{Na}^+), Sulfate (\text{SO}_4^{2-}), Magnesium (\text{Mg}^{2+}), Calcium (\text{Ca}^{2+}), and Potassium (\text{K}^+). Their proportions remain relatively constant due to the principle of conservation of ratios.