---
name: Oceanography and Geography
route: /2018/fall/bi360/week1/2
menu: BI 360
order: 3
---

# Oceanography and Geography

## Vocabulary

| **Word**         | **Definition**   |
| ---------------- | ---------------- |
| Halocline        | Area where density rapidly increases with depth due to increased salinity.|
| Pycnocline       | Any area where density changes rapidly with depth. Can be caused by rapid salinity and / or temp change.|
| Thermocline      | A layer of water where temperature decreases rapidly with depth. |
| Coriolis Effect  | There are different rotational speeds at differnt points along the earth. An object floating at the equator is travelling at a greater speed than the same object at the poles. An object moving from high speed area to low speed area will be deflected. If object is moving from South to North, it will be deflected East. If object is moving from North to South, it will be deflected West.|
| Gyre      |  |
| Ekman Transport      |  |
| Upwelling      |  |
| Downwelling      |  |
| Pelagic Division      |  |
| Active Swimmer      |  |
| Passive Swimmer      |  |
| Neritic Province      |  |
| Oceanic Province      |  |









## Present Day Ocean

- Geography of ocean floor and land masses

## Water Movement Impacted by Many Forces
- Water Density
  - Temperature / salinity impact Density

### The Importance of Density
- Drives water and also air circulation
  - Heavy air / water sinks
  - Light air / water rises
- Water
  - Density is a function of temp and salinity
  - Up density with down temp
  - up density with up salinity
  - changes in density cause water to sink/rise accordingly
Temperature plays primary role in ocean water density.
**Thermocline** - a layer of water where temperature decreases rapidly with depth.
- occurs when mixing is insufficient to transfer solar heat deeeper.
- change in density can act as a physical barrier.
- below this, temps are pretty stable.

## Density and Ocean Water

> Any type of **pycnocline** inhibits water mixing.

## Water Movement

### 2 Main Types of Currents are Driven Differently by Physical Factors

| **Surface Currents**         | **Deep Water Currents**  |
| ---------------- | ----------------|
| `10%` of ocean water                                                           | `90%` of ocean water      |
| Occur in upper `400m`                                                          | Move by density-driven forces (*Thermohaline*)      |
| Driven largely by external physical factors (wind / surface temps)             |       |

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## Surface Currents
1. Impact of wind
2. Impact of temperature
3. **Coriolis Effect**
4. Geography

### Impact of Wind
- density also drives air circulation.
  - Warm air rises, cools, gets more dense, and falls back down.
- Influenced by temperature, water, vapor, and atmospheric pressure.
  - increase temp = decrease density (*warm air rises*)

Dense air at poles sinks.
Large scale high/low pressure systems create winds that impact physical force on water.
- Wind generates friction where water / air meet.
- Produces waves.

### Impact of Temperature
Increased temp and wind create hills of water in ocean basins.
Gravity pulls water down the "hills".
Instead of moving down in a straight line, it is deflected to the right or the left. <- **Coriolis Effect*.

### Geography
The shape of the oceanic basin. Steep vs shallow. It all impacts the water.
5 major **gyres**.

### Ekman Transport
1. Wind pushes surface water.
2. Surface waters "drag" deeper waters with them.
3. Each layer of water is moved by friction.
4. Each deeper layer moves more slowly -> loss of energy.
5. Deflection of the surface current is `45°` due to the Coriolis Effect
6. At `100m`, water is transported roughly perpendicular to surface current flow.

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## Deep Water Currents

### Upwelling and Downwelling

**Downwelling**
- Water can sink, generally due to changes in density or the presence of convergence zones.

**Upwelling**
- Water pulled offshore and replaced by colder, more nutrient rich water.

### Upwelling in the PNW

#### An Eastern Boundary Current Upwelling System

### The Ocean Conveyor Belt System
- As warm water moves Northward, it loses heat and density increases.
  - Releases heat into air.
  - Cold water sinks (Downwelling)
  - Moves into other basins as deep water flow
  - Deep water pushed southward toward antartica.

#### Conveyor Belt and Global Warming
- Transport of heat partiallly moderates cold temperatures in the North.
- As Global warming increases temp at poles, melted freshwater enters the ocean.

### Movement of Water Impacts Organismal Connectivity

### Pelagic Division
- Ecosystems are those found in the open water.
  - Classified largely by depth and physical characteristics.

1. **Neritic Province**
2. **Oceanic Province**

#### Pelagic Organisms
- Spend almost all their adult life swimming (no prolonged contact with the bottom)
- Includes active and passive swimmers.

### Benthic Division

#### Benthic Organisms
- Spend most of their time living [----]