Ocean Acidification. The Basic Knowledge.

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Benedict Powers
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1 Ocean Acidification The Basic Knowledge.

2 Background Info Review ph measures the concentration of hydronium H 3 O + compared to hydroxide HO in a solution. Hydronium is a water molecule with a loosely bonded H +. Hydroxide is a water molecule missing an H +. ph is measured on a logarithmic scale. A solution of ph 2 is 10 times more acidic than a solution with ph 3.

3 PURE water is a 7 on the ph scale Earth s oceans are naturally registered over a ph of 8. Why not 7? Are our oceans acidic or alkaline? Alkaline means (basic).

4 What does Ocean Acidification Mean? Ocean Acidification does NOT mean the ocean is becoming an acid. It means the balance between H 3 O + and HO is shifting to a higher concentration of H 3 O +. The ocean, by having more H 3 O + than it did, is becoming LESS alkaline. Less alkaline is the same thing as more acidic. Ocean is not turning into an acid (solution with ph less than 7), but it IS changing in a dangerous way.

5 How to measure Ocean ph Models of the ocean s ph have been created using satellite imaging data, and checked with hand-collected data from researchers on ships around on the world. We will use that data for today s activity.

X-axis = longitude Y-axis = latitude This is a false-color

6 Map 1 ph for January 2008 The map shows an area of the Caribbean just northeast of Cuba and southeast of Florida. X-axis = longitude Y-axis = latitude This is a false-color map (it has a key where different colors represent different ph).

7 Map 1: ph for January 2008

8 Discuss in Groups 1. Where on this map is water less alkaline (more acidic?) a) What does that mean about concentrations of hydronium and hydroxide? 2. Where is the water more alkaline? a) What does that mean about hydronium and hydroxide concentrations?

9 Map 2 ph for August 2008

10 Place Map 1 and 2 side by side, then answer and discuss: 1. Is the water more alkaline or more acidic in August than in January? 2. What evidence is there on the maps for this conclusion?

11 Graph 1 X-Axis = time, months of the year 2008 Y-Axis = ph Each month has 1 data point, from the 15 th of the month (the middle) This map is for one single location. This location is the center of the false-color map.

12 Graph 1: Time-series ph changes 2008

13 Discuss Graph 1: 1. Does the change in ph reflect what you observed about the two false-color maps for January and August 2008? 2. In what months is the water the most alkaline? 3. In what months is the water the most acidic?

14 Graph 2 Sea-Surface Temperature 2008

15 Place Graph 1 and 2 side by side, then answer and discuss: 1. Does the temperature data support the idea that lower ph is linked to warmer surface water temperatures? 2. What does warmer water mean about the speed of ocean molecules?

16 ph and logarithmic scale review: Small changes in ph can represent larger changes in hydronium concentration Recall: a change of 1 ph represents a 10 times difference in the amount of hydronium. A decrease in ph of 0.1 is equivalent to about a 26% increase in H 3 O +.

17 Graph 3: ph time-series Graph

18 The Driving Forces of Ocean Acidification The phiner Points.

20 The Carbon Cycle The recycling of organic and inorganic carbon as it moves between Earth s Biosphere: Geosphere: Hydrosphere: Atmosphere:

21 Carbon Cycle Cont. The Carbon Cycle is a natural process where carbon transitions between the different spheres. Naturally, it would be 1 part of carbon into the atmosphere (as CO 2 ), and 1 part of carbon out of the atmosphere. How? List at least 1 way that you know carbon can leave the atmosphere.

22 Carbon Cycle Cont. Human activity currently adds more carbon to the atmosphere than can be taken out by all natural processes. We said that plants (the biosphere) takes some CO 2 out of the atmosphere. It turns out, the ocean takes a full 1 of all carbon. 3 The ocean is therefore called a carbon sink.

23 Ocean a Carbon Sink As we burn more carbon products and release more CO 2 into the atmosphere, the ocean takes in more CO 2. This CO 2 turns into a weak acid called carbonic acid (H 2 CO 3 )

24 ph change over 22 years Y-Axis is ph. X-Axis is time in years split into months.

25 Graph 3: ph time-series Graph

26 Analyze, Discuss, Answer 1. What has happened to ph over 22 years? 2. Is ph related to the seasons? If so, how is it related? 3. Why do you think the ph trend is what it is? 4. What do you expect has been happening to SST (sea surface tempts) over the years?

27 Graph of SST since 1980 Y-Axis is temperature in. X-Axis is time in years.

28 Graph 4: Temperature time-series Graph

29 Analyze, Discuss, Answer 1. Place the graphs side-by-side. What do you notice about SST in relationship to ph? 2. Is there a trend of SST on this graph? If so, what is it? 3. Does your answer to #2 support your observations of changing ocean ph?

30 Maps of May 1990 and May 2010 Each false-color map is of the same location that we studied last class. Color represents temperature in.

31 Map 3: Temp for May 1990

32 Map 4: Temp for May 2010

33 Analyze, Discuss, Answer 1. What differences in temperature do you observe between the two maps? A. Find an area where water is warmer. B. Find an area where water is cooler. 2. What seemed to happen to the majority of this ocean region?

34 So why becoming less alkaline? Recall: how acidic or alkaline a solution is is based upon its concentrations of H 3 O + and HO. We connected higher temperature to more H 3 O +. Higher temp is atoms moving faster, this cannot create H 3 O + from nothing.

35 So where does acid come from? When CO 2 is added to H 2 O, it forms carbonic acid: CO 2 + H 2 O H 2 CO 3 The sign means that this reaction can happen both ways. We ll explore just the creation of carbonic acid.

36 Carbonic Acid does What? Creation of carbonic acid CO 2 + H 2 O H 2 CO 3 Then there is H 2 CO 3 in water. That almost instantly dissociates in the seawater, releasing H + and bicarbonate molecules. H 2 CO 3 H + + HCO 3 Those H + loosely bond to water to make hydronium ions. H + + H 2 O H 3 O +

37 Think, Discuss, Answer 1. Based on what we ve learned, why do you think the average ph of a raindrop is 5.6?

38 What sources add CO 2 to Earth s atmosphere? Do you think any of these CO 2 sources have changed over time?

39 Compare both graphs of today with a new graph: Y-Axis is amount of CO 2 absorbed by our ocean. X-Axis is time in years.

40 Graph 5: Concentration of CO 2 absorbed time-series Graph

41 Analyze, Discuss, Answer 1. Ignoring the seasonal fluctuations, describe the overall trend in ph over time. 2. Describe the overall trend in sea-surface temperature over time. 3. Describe the overall trend in pco2sw over time. 4. What might cause an increase in dissolved CO2 in the ocean (and the resulting increased ocean acidity)?

Ocean Acidification the other CO2 problem..

Ocean Acidification the other CO2 problem.. Recall: Atm CO 2 already above recent planetary history CO 2 Today: What does this do to ocean water? Main Outline: 1. Chemistry. How does ocean absorb CO 2,