Question

27) (6 pts) We saw in class (and in the plot below, from class) that when concentration of the chemical compound MSA (methane sulfonic acid) is high in ice cores, the temperature of the Earth is low (and vice versa). MSA is an oxidation product of dimethylsulfide (DMS). Age ky ago 566 13 33 107 11 141 Work A) What is the source of the DMS that leads to MSA? (circle one) a) Marine algae b) Volcanic activity c) Power plant emissions d) Flatulent cows 8. SA ppt) B) Is the concentration of MSA consistent with the idea of a more efficient ocean biological pump during ice ages? (circle one) 1500 2000 1000 Desthom a) Yes b) No Bout ! AR 28) (5 pts) The maps to the right show the concentration of nitrate (top map) and the concentration of oxygen (bottom map) in the 60 deep oceans. Remember thermohaline circulation for deep ocean water. Why is nitrate low in the north Atlantic, but high in the north Pacific, whereas oxygen is high in the north Atlantic but low in the north Pacific? (circle one) a) Because salinity depletes ocean water in organic matter as it circulates through the deep oceans. O E E TUE 120 W b) Because of organic matter raining down from the surface as the deep ocean water circulates, giving off nitrate as it decays while being oxidized by oxygen (leading to oxygen consumption) EG c) This is because of toxicity in the deep oceans Atrios caused by the K/T impact event. d) This is because, 2000 years ago, the water The x 2 2 00 Austral sinking in the north Atlantic had less oxygen in it because of the last ice age. 2020 e) Both cand d are true E 120E TE Longitude Latitude 28 180S 940 Av. Longitude

Answer 1

1. Dimethyl sulphide (DMS) is produced by bacterial degradation of dimethylsulfoniopropionate (DMSP) which is abundant in marine algae. DMS is associated with the aerosol formation which influences the global weather through its negative forcing.

DMSP is an organo-sulphur compound common in marine phytoplankton, seaweeds and other aquatic plant species. It is degraded by bacterial action to form 2 volatile compounds one of which is DMS.

2. The increased concentration of MSA is totally in sync with a more efficient ocean biological pump during Ice ages. With Ice age in progress, ocean water was cooled. Hence their carbon dioxide holding capacity increased phenomenally. With more carbon dioxide stored I the water, marine phytoplankton proliferated leading to the increased production of DMSP. DMSP was later degraded to form DMS which was further oxidised to produce MSA.

Concluding, with increased efficiency of biological pump (increased carbon sequestration in the oceans) MSA concentration increased in the oceanic water (mostly polar regions).

3. (B) Due to Thermohaline circulation similar to the oceanic conveyor belt, Atlantic Ocean loses deep water to the Pacific Ocean and receives surface water from central and south Atlantic as well as water from Greenland. This surface water is relatively poor in nutrients, while the deep waters sent to pacific is high in the nutrient. This leads to a low nutrient in Atlantic and high nutrients in the Pacific.

Moreover, the young Atlantic water has plenty of oxygen while the oxygen content in old pacific water is low since the oxygen has been used up for oxidation and decay purpose.