Lecture #5 (Hydrosphere) Flashcards
How much of the Earth’s surface is covered in water? And how much of it is freshwater?
70%; 1%
Out of the 1.4 billion cubic kilometers of water on Earth __% is seawater and is therefore not useable for humans
97
What 2 factors drive the Water Cycle?
Solar energy and gravity
Define evaporation
The process of turning from liquid to vapor
Define groundwater
Water held underground in the soil or in pores and crevices in rock
Define aquifers
A body of permeable rock which can contain or transmit groundwater
What is water ‘recharge’ rates?
How long it takes for water to be contributed back to the aquifer
What is the largest reservoir of water on Earth?
Oceans
_____ are based on depth and corresponding water temperature
Oceanic divisions
What is the photic layer of the ocean?
The first 200m where light can still penetrate the water
The photic layer is also known as what?
The epipelagic layer
From 200m depth to where water temperature is 10C (~1000m) is known as the _____ layer
Mesopelagic
What layer of the Ocean is between 10C and 4C?
Bathypelagic layer
What layer of the Ocean is from 4C to 6000m depth?
Abyssalpelagic
What layer is below 6000m?
Hadalpelgic
What does the term pelagic refer to?
Anything relating to the open seas
What is the order (highest to lowest) of the Oceanic divisions?
Epipelagic; Mesopelagic; Bathypelagic; Abyssalpelagic; Hadalpelagic
What is the thermocline?
The rapid decline in temperature over a fairly narrow change in depth (directly below the mixed layer)
What is the mixed layer of Oceans?
The first 100m - 200m of the Ocean where the temperature is fairly constant due to surface winds, waves, and currents mixing the upper water and distributing the heat throughout the layer
Typical temperature profile for open ocean, mid-latitude water is what?
~2C (varies little over time)
Why is there a larger thermocline in tropics than polar areas?
Due to surface water being warmer near the equator and colder at the poles
The mixed layer is deeper, and the thermocline is less pronounced in the winter compared to the summer in what regions of the ocean?
Temperate (mid-latitude) regions
What areas have the largest seasonal changes?
Temperate (mid-latitude) regions
At the lowest latitudes water is the _____
warmest
At higher latitudes water is the _____
coldest
What are the 2 types of freshwater systems?
Lentic and Lotic
What are lentic freshwater systems?
Still or un-flowing water (lakes, ponds, marshes, swamps, bogs, etc.)
Len think zen = still
What are lotic freshwater systems?
Flowing water (rivers and streams)
Lo think flow = flowing
Limnology is the study of what?
Freshwater systems
What are some properties of oligotrophic lakes?
Low levels of nutrients and thus lower productivity (normally clear water); normally deeper; fewer phosphates & nitrates present as nutrients leading to high levels of oxygen; more growth of green algae & less blue green algae
What are some properties of eutrophic lakes?
Large amounts of nutrients & thus higher productivity (often turbid/dark water); relatively shallow; has nutrients like phosphates & nitrates in large quantities making it difficult for some aquatic life as these nutrients lead to low levels of oxygen; eutrophic lakes have more growth of blue green algae & less green algae
What is cultural eutrophication?
When the rate of eutrophication is rapidly accelerated by the addition of nutrients & organic matter from human activities
An overgrowth of algae that blocks light & air exchange can be caused by what?
Cultural eutrophication
What are dimictic lakes?
Lakes that ‘mix’ twice a year; typically, temperate & boreal regions lakes
What is a thermocline?
The boundary area where temperature changes are drastic over short depths
What is stratification?
The arrangement or classification of something into different groups (warm water at the surface & cooler below)
Lakes are at a constant __C in the water column
4
What happens in the spring during circulation in temperate lakes?
Mixing or turning over of a lake when surface temps reach 4C (constant density)
What happens in the summer during circulation in temperate lakes?
Heating of surface creates a strong thermocline separating cool, deep water from warm water; mixing occurs only above thermocline
What happens in the fall during circulation in temperate lakes?
Mixing or turnover of a lake when surface temps reach 4C (constant density)
What happens in the winter during circulation in temperate lakes?
Winter ice prevents mixing; coldest water (& ice) at surface, warmest & denser water at bottom
When lakes are stratified (i.e. in the presence of a thermocline), 3 layers are formed. What are the 3 layers?
1) Epilimnion
2) Metalimnion
3) Hypolimnion
What is the epilimnion?
The surface layer of water that is constantly mixed by wind and waves and is warmed by the sun, from late spring to late fall.
What is the metalimnion?
The middle layer characterized by a steep gradient in temperature and demarcated by the regions above (epilimnion) and below (hypolimnion). The metalimnion is the barrier that prevents mixing and heat exchange between the epilimnion and hypolimnion
What is the hypolimnion?
The deepest layer of uniformly cold water that does not mix with the upper layers and has low circulation. The colder water within the hypolimnion is at its maximum density at a temperature of 39.32F (4C)
At what temperature is freshwater most dense?
4C
What is Langmuir circulation?
‘Cells’ of water with circular/rotational movements of water forming surface foam lines that run parallel to the direction of wind. The turbulence circulates nutrients in the water column & are important for mixing nutrients in the upper layer.
What is evapotranspiration?
The combination of evaporation & transpiration in plants
Are areas of high precipitation, plant biomass & warmth are associated with areas of high or low evapotranspiration?
High
What are some sources of water contamination?
Point-source; air pollution; eroded soil and sediment; non-point source
What is point-source pollution?
Contamination can be traced to specific points of discharge from wastewater treatment plants and factories or from combined sewers
How is air pollution a source of water contamination?
It spreads across the landscape and is often overlooked as a major nonpoint source of pollution. Airborne nutrients and pesticides can be transported far from their area of origin.
How is non-point source pollution a source of water contamination?
It is much more difficult & expensive to control than point source pollution because of its low concentration, multiple sources, & greater volume of water
How is eroded soil and sediment a source of water contamination?
It can transport considerable amounts of some nutrients, such as organic nitrogen and phosphorus, and some pesticides, such as DDT, to rivers and streams
What is another source of water contamination? (Think of urban centers when it rains)
Combined sewer system - combines sewer with storm drain
