1. Ocean Chemistry and Circulation
By this time, you’re familiar with the Hawaii Ocean Time-series and interpreting horizontal profiles of temperature, phytoplankton, and nutrients at Station ALOHA. Now we are going to introduce vertical depth profiles at Station ALOHA and see how ocean processes in the Pacific Ocean relate to global scales of circulation. In other words, how do oxygen concentrations vary from the ocean surface to depth, and why? How do processes such as the formation of deep water in the Atlantic Ocean affect nutrient cycling in the Pacific Ocean? Let’s take a look! (click)

2. Vertical Profiles  Display  Bottle
Photosynthesis
Gas exchange
Respiration
Decomposition
Deep ocean circulation
Respiration
Decomposition
On HOT-DOGS, we can examine how a variable, such as oxygen, changes from the surface to the deep ocean by choosing a vertical depth profile. If we select a vertical profile of oxygen (click) from the surface to 5000 m depth (click), we can see that oxygen concentrations are highest near the ocean surface (click) where oxygen-producing phytoplankton are most abundant and where the ocean exchanges gases with the atmosphere. Organisms that live throughout the water consume oxygen as they feed on phytoplankton and other cells, therefore oxygen concentrations (click) decrease with depth to about 800 m.
Deeper than 800 m (click), oxygen concentrations (click) increase with depth because the deep Pacific Ocean is supplied with oxygen-enriched water from the Atlantic. Also, the abundance of organisms decreases with depth, so less oxygen is consumed in the deep ocean than in the surface ocean.
The oxygen profiles of these two layers (click) appear quite different because the density differences between the upper and deep ocean inhibit mixing. The oxygen profile for the upper ocean (click) is affected mostly by phytoplankton productivity, gas exchange with the atmosphere, respiration, and decomposition, while the oxygen profile for the deep ocean (click) is determined mostly by deep ocean circulation, respiration, and decomposition.
Vertical and horizontal profiles on HOT-DOGS can tell us a lot about what is happening in the North Pacific, but what about other locations? (click)
Vertical Profiles  Display  Bottle 2

3. Two Time-series Stations
1. Hawaii Ocean Time-series (HOT)
- Station ALOHA
- Pacific Ocean
2. Bermuda Atlantic Time-Series (BATS)
- Station BATS
- Atlantic Ocean
In addition to the Hawaii Ocean Time-series (click) in the North Pacific Ocean, there is also a long-term oceanographic study in the Atlantic Ocean near Bermuda. This research program is called the Bermuda Atlantic Time-series, or BATS. (click)

4. A Comparison: Pacific vs. Atlantic
Similar to the HOT program, data from the BATS program are available online. Downloading data from both sites allows us to compare variables in the Pacific and Atlantic Oceans and to better understand large-scale ocean processes. (click)

5. Respiration/ Decomposition
Organisms consume oxygen during respiration and feeding
Deep ocean circulation
- Water “ages” as it moves from Atlantic to Pacific
- Oxygen is depleted over time
For example, you may download oxygen and depth data from both the Atlantic and Pacific Oceans and plot them in Excel. Differences in oxygen concentrations between the Pacific and Atlantic Ocean basins are controlled by a combination of respiration (click), decomposition, and thermohaline circulation. As you saw earlier, oxygen concentrations in the surface ocean decrease with depth (click) because organisms have more time to consume oxygen as they respire and feed on organic matter.
This graph of oxygen versus depth shows that deep water in the Pacific has much less oxygen than that in the Atlantic. The surface water in the North Atlantic is oxygen-rich when it starts to sink, at which time it is considered to have an age of zero years. As this water travels in the deep ocean current to the Pacific, more and more oxygen is removed over time by organisms as they feed and respire. The deep water “ages” as it flows from the Atlantic to the Pacific where the deep water resurfaces (click). Pacific deep water is several hundred years “older” than Atlantic deep water (click), and organisms have had much more time to use up oxygen during respiration and feeding.
Now it’s your turn! Using nutrient data from the HOT and BATS programs, you will plot and compare nitrogen concentrations in the Pacific and Atlantic Oceans. (click) 5