海洋科學(xué)導(dǎo)論-9-朱彤

1、海洋科學(xué)導(dǎo)論,第九講 海-氣作用及化學(xué)過(guò)程,環(huán)境科學(xué)與工程學(xué)院朱彤,2014年4月1日,1,1. 為什么關(guān)注海氣作用？2. 海洋向大氣釋放的物質(zhì)及影響？3. 大氣沉降對(duì)海洋的影響？4. 污染物的海氣交換及其對(duì)海洋環(huán)境的影響5. 海洋吸收CO2的后果？海洋酸化6. 可否利用海氣物質(zhì)交換控制氣候變化？海洋施鐵（肥）實(shí)驗(yàn)7. 如何準(zhǔn)確測(cè)量海氣交換通量？,第九講 海-氣作用及化學(xué)過(guò)程,2,為什么關(guān)注海氣作用？,地球可分為大氣、

2、巖石、生物、水（包括海洋）、冰凍、人類等多個(gè)圈層。圈層間密切作用，影響。,3,地球的圈層間密切作用、影響，構(gòu)成地球系統(tǒng)。,4,地球圈層間的相互作用，形成影響氣候、環(huán)境的正、負(fù)反饋過(guò)程,5,地學(xué)研究的前沿領(lǐng)域：發(fā)展地球系統(tǒng)模式，模擬圈層間相互作用,6,海氣作用在氣候變化、海洋生態(tài)系統(tǒng)、生物地球化學(xué)循環(huán)中有著重要影響,7,海氣相互作用，主要指發(fā)生在大氣下層1000米（邊界層）和海洋上層100-1000米之間物質(zhì)和能量的交換，本次課程主要介紹

3、物質(zhì)交換及其影響。,8,海氣物質(zhì)和能量交換：碳，鐵，氮，硫，磷，錳，鹵素，氧氣，水，熱，動(dòng)量相關(guān)學(xué)科：大氣化學(xué)/物理，氣候，海洋物理，海洋生物系統(tǒng)，海洋生物地球化學(xué),9,2.海洋向大氣釋放的物質(zhì)及影響？,10,CLAW假說(shuō)：海洋釋放DMS對(duì)全球氣候和環(huán)境的影響海氣作用與氣候變化的負(fù)反饋,11,海洋浮游生物的生理過(guò)程會(huì)釋放出二甲基硫，進(jìn)入大氣后會(huì)被氧化為硫酸鹽，促進(jìn)云的形成。,12,Woods Hole Oceanographic I

4、nstitution,海洋氮循環(huán)：硝化與反硝化的副產(chǎn)物氧化亞氮N2O是溫室氣體海氣作用與氣候變化的正反饋,13,海水也是溫室氣體甲烷的一個(gè)來(lái)源。此外，海洋中存在著大量的甲烷水合物，既是一種未來(lái)的能源，也是溫室氣體的一個(gè)潛在的來(lái)源,14,衛(wèi)星遙感監(jiān)測(cè)全球大氣中甲烷濃度的分布,15,極地冰凍層釋放甲烷：海氣作用與氣候變化的正反饋,16,3.大氣向海洋輸送的物質(zhì)及影響,17,Illustration by Jack Cook, Woods

5、Hole Oceanographic Institution,海洋的光合作用與固氮作用,18,大氣物質(zhì)沉降影響海洋初級(jí)生產(chǎn)過(guò)程,19,20,Model-estimated anthropogenic (1990–2000 minus preindustrial) atmospheric deposition fluxes for carbon, nitrogen, and sulfur (molm2y1); alkalinity; an

6、d potential alkalinity, assuming complete nitrification of NH4 + NH3 (eq m-2y-1).,Doney et al. PNAS September 11, 2007 vol. 104 no. 37 14583,21,Perturbation maps of simulated surface water pH, DIC, and total alkalini

7、ty trends and air–sea CO2 flux due to anthropogenic atmospheric nitrogen and sulfur deposition.,Doney et al. PNAS September 11, 2007 vol. 104 no. 37 14583,22,4. 污染物的海氣交換及其對(duì)海洋環(huán)境的影響,WATCONChemicals in Inland and Marin

8、e Waters,Simulation of bioaccumulation and ecological risk in aquatic ecosystems,23,Illustration by Jack Cook, Woods Hole Oceanographic Institution),24,The biogeochemical cycling of mercury. Deposition of Hg to the ocean

9、 is primarily as Hg(II). A substantial amount (roughly 1/3) of the deposited Hg is returned to the atmosphere following reduction of Hg(II) to Hg(0). Bioaccumulation of Hg occurs mostly through the retention of monomethy

10、lHg (MMHg) in biota. Most of the Hg entering the ocean is not methylHg, however, and complex biological and abiological processes result in the formation of MMHg and dimethylHg (DMHg).,25,Monomethylmercury (MMHg) is the

11、toxic form of mercury that accumulates up the food chain into fish. High levels of MMHg are found at mid-water ocean depths where oxygen levels are lowest. Are bacteria making MMHg in the open ocean as they do in sedimen

12、ts closer to land, or are other complex processes going on? To probe this mystery, scientists collected hundreds of seawater samples above and in the low-oxygen zone. (Jack Cook, Woods Hole Oceanographic Institution),26,

13、27,5. 海洋吸收CO2的后果？海洋酸化！,Riccardo Pravettoni, UNEP/GRID-Arendal,28,29,30,Global climatology of the annual net air-sea CO2 flux based on interpolation of air-sea pCO2 differences referenced to the year 1995 (Takahashi et al

14、., 2002).,31,Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s,http://en.wikipedia.org/wiki/File:WOA05_GLODAP_del_pH_AYool.png,32,海洋酸化的后果,33,34,Cavernous Star Coral (Montastrea caverno

15、sa) in the Florida Keys National Marine Sanctuary. Photo: Florida Keys National Marine Sanctuary Staff.,State of the Science FACT SHEET, NOAA,35,Scanning electron microscope pictures of coccolithophorids grown under low

16、and high CO2 conditions, corresponding to pCO2 levels of about 300 ppmv (a-c) and 780-850 ppmv (d-f). Note the difference in the coccolith structure (including malformations) and in the degree of calcification of cells g

17、rown at normal and elevated CO2 levels (Riebesell et al., 2000).,36,Photomicrographs of the shell of the pteropod, Clio pyramidata, collected from the subarctic Pacific. (a) Whole shell from a live pteropod kept in corro

18、sive seawater for 48 hours; the white rectangle indicates the location of the magnified area in (b), which shows advanced dissolution along the leading edge of the shell. (c) No dissolution is observed at the leading edg

19、e of shell from Clio pyramidata kept in non-corrosive seawater (photos from V. Fabry).,State of the Science FACT SHEET, NOAA,37,http://www.whoi.edu/OCB-OA/page.do?pid=40276,38,Potential impact of rising atmospheric CO2 o

20、n coral reef calcification rate.,State of the Science FACT SHEET, NOAA,39,6. 可否利用海氣物質(zhì)交換控制氣候變化？海洋施鐵（肥）實(shí)驗(yàn),40,Ocean Fertilization A scientific summary for policy makers, SOLAS,41,Got iron? It's an essential nutrient fo

21、r living things, but it's scarce in the ocean. Scientists have found that a key marine bacterium may have evolved a remarkable biochemical way to recycle it and reduce its iron requirments by half. (Illustration by J

22、ack Cook, Woods Hole Oceanographic Institution,42,43,IRON ADDITIONS, NATURAL AND EXPERIMENTAL—Left, a plume of dust from glacial sedimentsin Alaska blows far into the North Pacific Ocean. Storms like this, or from vast

23、deserts such asthe Sahara, are the natural way that iron gets into oceans to fertilize phytoplankton blooms.Right, a bloom resulting from an intentional addition of iron in roughly the same region(during the experimen

24、tal Subarctic Ecosystem Response to Iron Enrichment Study in 2002)shows up in the bottom center of the satellite image below as a red patch (indicating high levelsof chlorophyll from the microscopic marine plants).,44,

25、IRON EXPERIMENTS OFF ANTARCTICA—Scientists aboard the Australian research vessel Aurora Australis studied the natural cycling of iron in the Southern Ocean in 2001. Ken Buesseler, a marine chemist at Woods Hole Oceanogra

26、phic Institution, was aboard that expedition, and in 2002 he served as chief scientist of the Southern Ocean Iron Experiment (SOFeX). The three-ship operation investigated the results of adding iron to stimulate a phytop

27、lankton bloom in the Southern Ocean.,45,TESTING THE WATERS—Twelve small-scale experiments over the past decade in several ocean locations (red dots) consistently showed that intentional iron additions do result in phytop

28、lankton blooms that help draw down carbon dioxide from the air. But the experiments have not determined how much carbon is transferred and sequestered in the deep sea, rather than quickly recycled back to the atmosphere.

29、,10 Oceanus Magazine Vol. 46, No. 1, 2008 www.whoi.edu/oceanus,46,FROM TOXINS TO CLOUDS—The addition of iron to the oceans could stimulate algal blooms that might be harmful or beneficial. Some scientists caution that ir

30、on fertilization could favor certain species of the marine diatom, Pseudo-nitzchia (top), which can sometimes produce domoic acid, a toxin harmful to animals and humans. On the other hand, algae called coccolithophorids

31、(bottom) release dimethyl sulfide, which eventually encourages cloud formation in the atmopshere that can block solar radiation and help cool the planet.,BLOOMS AND DEAD ZONES—One concern about iron-fertilized phytoplank

32、ton blooms is that they eventually could lead to waters devoid of life—a process that can also occur naturally. In coastal waters off southwest Africa, easterly winds push surface water away from the shore, allowing cold

33、, deep, iron- and nutrient-rich waters to rise to the surface and stimulate blooms, such as this one (the blue-green patch captured by a NASA satellite image) that stretched for hundreds of kilometers off Namibia in Nove

34、mber 2007. But when large amounts of marine plants die, bacteria decompose them, using up some of the oxygen available in the water and sometimes creating anoxic “dead zones” where fish can’t survive.,14 Oceanus Magazine

35、 Vol. 46, No. 1, 2008 www.whoi.edu/oceanus,47,10 Oceanus Magazine Vol. 46, No. 1, 2008 www.whoi.edu/oceanus,48,SAVED BY THE SALPS??Another proposed scheme to reduce CO2 levels would promote swarms of transparent animals

36、called salps, whose heavy fecal pellets sink fast, ferrying carbon to the depths. (Photo by Laurence Madin, Woods Hole Oceanographic Institution) [back],49,How long will carbon be sequestered in the ocean?How deep is de

37、ep enough to accomplish this?How can sequestration efficiency be increased?How does the ocean food web change during and after a bloom?Which phytoplankton and grazers raise sequestration efficiency?Which parts of the

38、 ocean are best for iron fertilization?What size and what shaped patch should be fertilized?How often and how continually should iron be added?What kinds of currents and surface conditions give the best results?How c

39、an the amount and fate of carbon from a bloom be verified?How can effects downstream of experiments be detected?How can the production of other greenhouse gases be monitored?,海洋施鐵（肥）的問(wèn)題,50,TUBING THE OCEAN? Increasing

40、urgency about climate change has spurred proposals, which may have seemed radical not too long ago, to reduce atmospheric carbon dioxide levels. In a recent issue of the journal Nature, scientists James Lovelock and Chri

41、s Rapley proposed putting thousands of giant plastic tubes in the ocean. Wave motion and a one-way valve would push deep water through the tubes to the surface, bringing up essential nutrients to stimulate blooms of tiny

42、 marine plants. These phytoplankton would help draw down heat-trapping carbon dioxide from the air and also emit a chemical called dimethyl sulfide, which stimulates the formation of clouds that would block solar radiati

43、on and help cool the planet, the scientists say. (Illustration by Jack Cook, Woods Hole Oceanographic Institution),51,7. 如何準(zhǔn)確測(cè)量海氣交換通量？,52,海-氣界面通量的估計(jì)存在的問(wèn)題,目前算出的海-氣通量交換系數(shù)（拖曳系數(shù)、氣體交換速度、熱量交換系數(shù)、水汽交換系數(shù)）僅以海上風(fēng)速為參量，得出的結(jié)果相當(dāng)分散。,熱交換通

44、量,53,二氧化碳通量估計(jì)的不確定性,根據(jù)Takahahshi et al. (1997)的估計(jì)，使用不同作者給出的公式，得到海洋每年吸收0.6~1.36 GtC/yr.Suzuki et al. (2001)用同樣的二氧化碳分壓數(shù)據(jù)，采用其他交換速度公式，得到的結(jié)果為2.3 GtC/yr.對(duì)其它海-氣界面通量計(jì)算存在同樣的問(wèn)題，因此對(duì)海-氣交換過(guò)程機(jī)制研究顯得十分重要。,,54,全球氣候變化,大氣-海洋界面過(guò)程,海氣界面交換過(guò)程

45、動(dòng)量、熱量水汽、氣體,波浪,,,,,風(fēng),,55,波浪及其破碎在海-氣界面交換中的作用,,,?,56,57,Key components to be measured to understand and extrapolate air-sea gas transfer to global and regional scales, SOLAS Science Plan,58,中國(guó)海洋大學(xué)大型風(fēng)浪槽,59,總結(jié)：1. 海氣作用在地球系統(tǒng)、

46、大氣海洋環(huán)境、氣候變化中發(fā)揮重要的作用。2. 海洋向大氣釋放的物質(zhì)影響大氣環(huán)境及氣候。3. 大氣沉降對(duì)海洋輸送營(yíng)養(yǎng)物質(zhì)（CO2、鐵、硝酸鹽），影響海洋生態(tài)系統(tǒng)。4. 多種污染物通過(guò)海氣交換影響海洋環(huán)境。5 大氣CO2濃度增加導(dǎo)致海洋酸化，進(jìn)而影響海洋生態(tài)系統(tǒng)。6. 通過(guò)海洋施鐵（肥），可以增加海洋生物生產(chǎn)力，增加對(duì)CO2的吸收，但全面實(shí)施的后果未知。7. 準(zhǔn)確測(cè)量海氣交換通量目前仍然是一個(gè)重要的挑戰(zhàn)。,第九講 海-氣作用及