海洋科学导论-9-朱彤

1、海洋科学导论,第九讲 海-气作用及化学过程,环境科学与工程学院 朱彤,2014年4月1日,1,1. 为什么关注海气作用？ 2. 海洋向大气释放的物质及影响？ 3. 大气沉降对海洋的影响？ 4. 污染物的海气交换及其对海洋环境的影响 5. 海洋吸收CO2的后果？海洋酸化 6. 可否利用海气物质交换控制气候变化？ 海洋施铁（肥）实验 7. 如何准确测量海气交换通量？,第九讲 海-气作用及化学过程,2,为什么关注海气作用？,地球可分为大气、岩石、生物、水（包括海洋）、冰冻、人类等多个圈层。圈层间密切作用，影响。,3,地球的圈层间密切作用、影响，构成地球系统。,4,地球圈层间的相互作用，形成影响气候、

2、环境的正、负反馈过程,5,地学研究的前沿领域：发展地球系统模式，模拟圈层间相互作用,6,海气作用在气候变化、海洋生态系统、生物地球化学循环中有着重要影响,7,海气相互作用，主要指发生在大气下层1000米（边界层）和海洋上层100-1000米之间物质和能量的交换，本次课程主要介绍物质交换及其影响。,8,海气物质和能量交换：碳，铁，氮，硫，磷，锰，卤素，氧气，水，热，动量 相关学科：大气化学/物理，气候，海洋物理，海洋生物系统，海洋生物地球化学,9,2.海洋向大气释放的物质及影响？,10,CLAW假说：海洋释放DMS对全球气候和环境的影响 海气作用与气候变化的负反馈,11,海洋浮游生物的生理过程会

3、释放出二甲基硫，进入大气后会被氧化为硫酸盐，促进云的形成。,12,Woods Hole Oceanographic Institution,海洋氮循环：硝化与反硝化的副产物氧化亚氮N2O是温室气体 海气作用与气候变化的正反馈,13,海水也是温室气体甲烷的一个来源。此外，海洋中存在着大量的甲烷水合物，既是一种未来的能源，也是温室气体的一个潜在的来源,14,卫星遥感监测全球大气中甲烷浓度的分布,15,极地冰冻层释放甲烷：海气作用与气候变化的正反馈,16,3.大气向海洋输送的物质及影响,17,Illustration by Jack Cook, Woods Hole Oceanographic In

4、stitution,海洋的光合作用与固氮作用,18,大气物质沉降影响海洋初级生产过程,19,20,Model-estimated anthropogenic (19902000 minus preindustrial) atmospheric deposition fluxes for carbon, nitrogen, and sulfur (molm2y1); alkalinity; and potential alkalinity, assuming complete nitrification of NH4 + NH3 (eq m-2y-1).,Doney et al. PNAS Se

5、ptember 11, 2007 vol. 104 no. 37 14583,21,Perturbation maps of simulated surface water pH, DIC, and total alkalinity trends and airsea CO2 flux due to anthropogenic atmospheric nitrogen and sulfur deposition.,Doney et al. PNAS September 11, 2007 vol. 104 no. 37 14583,22,4. 污染物的海气交换及其对海洋环境的影响,WATCON

6、Chemicals in Inland and Marine 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 is primarily as Hg(II). A substantial amount (roug

7、hly 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 monomethylHg (MMHg) in biota. Most of the Hg entering the ocean is not methylHg, however, and complex biological and abiological processes r

8、esult in the formation of MMHg and dimethylHg (DMHg).,25,Monomethylmercury (MMHg) is the 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 i

9、n sediments 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),26,27,5. 海洋吸收CO2的后果？海洋酸化！,Riccardo Pravettoni, UNEP/GRID-Arendal,28,29,30,

10、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., 2002).,31,Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s,/wiki/File:WOA05_GLODAP_del_pH_

11、AYool.png,32,海洋酸化的后果,33,34,Cavernous Star Coral (Montastrea cavernosa) 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 and high CO2

12、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 grown at normal and elevated CO2 levels (Riebesell et al., 2000).,36,Photomicrographs of the s

13、hell of the pteropod, Clio pyramidata, collected from the subarctic Pacific. (a) Whole shell from a live pteropod kept in corrosive 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

14、) No dissolution is observed at the leading edge of shell from Clio pyramidata kept in non-corrosive seawater (photos from V. Fabry).,State of the Science FACT SHEET, NOAA,37,/OCB-OA/page.do?pid=40276,38,Potential impact of rising atmospheric CO2 on coral reef calcification rate.,S

15、tate of the Science FACT SHEET, NOAA,39,6. 可否利用海气物质交换控制气候变化？ 海洋施铁（肥）实验,40,Ocean Fertilization A scientific summary for policy makers, SOLAS,41,Got iron? Its an essential nutrient for living things, but its scarce in the ocean. Scientists have found that a key marine bacterium may have evolved a rema

16、rkable biochemical way to recycle it and reduce its iron requirments by half. (Illustration by Jack Cook, Woods Hole Oceanographic Institution,42,43,IRON ADDITIONS, NATURAL AND EXPERIMENTALLeft, a plume of dust from glacial sediments in Alaska blows far into the North Pacific Ocean. Storms like this

17、, or from vast deserts such as the 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 experimental Subarctic Ecosystem Response to Iron Enrichment Study in 2002

18、) shows up in the bottom center of the satellite image below as a red patch (indicating high levels of chlorophyll from the microscopic marine plants).,44,IRON EXPERIMENTS OFF ANTARCTICAScientists aboard the Australian research vessel Aurora Australis studied the natural cycling of iron in the South

19、ern Ocean in 2001. Ken Buesseler, a marine chemist at Woods Hole Oceanographic 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 phytoplankto

20、n bloom in the Southern Ocean.,45,TESTING THE WATERSTwelve small-scale experiments over the past decade in several ocean locations (red dots) consistently showed that intentional iron additions do result in phytoplankton blooms that help draw down carbon dioxide from the air. But the experiments hav

21、e not determined how much carbon is transferred and sequestered in the deep sea, rather than quickly recycled back to the atmosphere.,10 Oceanus Magazine Vol. 46, No. 1, 2008 /oceanus,46,FROM TOXINS TO CLOUDSThe addition of iron to the oceans could stimulate algal blooms that might be ha

22、rmful or beneficial. Some scientists caution that iron 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 (bottom) release dimethyl su

23、lfide, which eventually encourages cloud formation in the atmopshere that can block solar radiation and help cool the planet.,BLOOMS AND DEAD ZONESOne concern about iron-fertilized phytoplankton blooms is that they eventually could lead to waters devoid of lifea process that can also occur naturally

24、. In coastal waters off southwest Africa, easterly winds push surface water away from the shore, allowing cold, 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

25、kilometers off Namibia in November 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 cant survive.,14 Oceanus Magazine Vol. 46, No. 1, 2008 /oceanus,47,10 Oc

26、eanus Magazine Vol. 46, No. 1, 2008 /oceanus,48,SAVED BY THE SALPS?Another proposed scheme to reduce CO2 levels would promote swarms of transparent animals called salps, whose heavy fecal pellets sink fast, ferrying carbon to the depths. (Photo by Laurence Madin, Woods Hole Oceanographic

27、 Institution) back,49,How long will carbon be sequestered in the ocean? How deep is deep 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

28、of the 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 can the amount and fate of carbon from a bloom be verified? How can effects

29、 downstream of experiments be detected? How can the production of other greenhouse gases be monitored?,海洋施铁（肥）的问题,50,TUBING THE OCEAN? Increasing urgency about climate change has spurred proposals, which may have seemed radical not too long ago, to reduce atmospheric carbon dioxide levels. In a rece

30、nt issue of the journal Nature, scientists James Lovelock and Chris 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 marine plants. These phytoplankton would help draw down heat-trapping carbon dioxide from the air and also emit a chemical called dimethyl sulfid