CHAPTER 12 THE OCEAN AND CLIMATE CHANGE

1. CHAPTER 12�THE OCEAN AND CLIMATE CHANGE

3. Caps OffA NASA satellite image from September 16, 2007 shows Arctic summer sea ice at its lowest level, shattering a record set in 2005. 

4. Out of their DepthOne of two dolphins, who are usually found in warmer waters, sighted in the Baltic Sea near Germany in September.

5. How realistic was the movie? It has a kernel of truth, although it has been "Hollywoodized." There is evidence that abrupt climate change has happened a couple of times in the last 13,000 years, but it's never happened in a few days, as it does in the movie. That's completely impossible.

6. What is the ocean conveyor belt referred to in the movie, and what is its importance to the Earth's climate? It's the system of currents that flows around the oceans of the world and carries heat from the tropics to the northern latitudes. There is evidence that the North Atlantic branch of the current has failed in the distant past�8,200 and 12,700 years ago�causing a great cooling of the climate.

7. In the movie, the influx of fresh water, caused by the melting of a massive ice sheet, changes the salinity of the oceans, shutting down the Gulf Stream. Could that happen? In theory, that is realistic. Salty water is heavier than fresh water. When the cold, salty current reaches the northern latitudes and gives out its heat, the current actually sinks and flows back along the bottom of the ocean toward the tropics. When then there's a lot of fresh water added to that current, it may stop flowing, because it's not dense enough to sink anymore. In the past, retreating glaciers dumped enormous amounts of fresh water very suddenly into the North Atlantic, and the currents stopped.

8. Many factors operating as components of Earth�s climate system govern the spatial and temporal variabilty of climate. Some of these factors vary in a regular and predictable way over short periods of time, others much longer. Solar radiation Greenhouse effect Cloud cover Volcanic eruptions El nino Earths surface properties (albedo) Elevation Latitude, Sea surface temperatures Sea ice cover

9. An example of climate control that varies in a regular and predictable way over the course of a year is (are) 1. (incoming solar radiation) (volcanic eruptions)

10. A factor that contributes in a significant way to the inter-annual (year to year) variability of climate in some areas of the globe is 2. (movement of tectonic plates) (El Ni�o)

11. An example of a climate control whose influence on the climate of a specific place remains essentially fixed over millions of years is 3. (latitude) (elevation) (distance from the ocean) (all of these)

12. Each of the various controls of climate are not independent of the others but linked in cause-effect relationships.

13. Ex: the albedo of the Earth�s surface determines the fraction of incident solar radiation that is reflected and hence, the remaining fraction that is absorbed and converted to heat. (the lower the albedo the greater the % of incident radiation absorbed and the warmer the surface�.so air temp over a high albedo surface (snow) is lower than over a low albedo surface (bare ground)

14. The sequence of interactions between climate controls determines how Earth�s climate system responds to some initial disturbance (or perturbation) of the system. These interactions constitue feedback in the system. A feedback that amplifies the final state of the system is called a positive feedback. A feedback that reduces the final state of the system is called a negative feedback.

16. Assuming rising levels of atmospheric carbon dioxide enhance the greenhouse effect, temperatures in the lower atmosphere will rise. Global climate models predict that the magnitude of the warming will be greater at higher latitudes. Amplification of the warming at higher latitudes is likely to shrink the sea ice cover in polar regions.

17. Higher temperatures have affected Arctic sea ice

18. The sequence of interactions among climate controls as described on the previous slides, (beginning with warming due to an enhanced greenhouse effect) is an example of potential 4. (positive) (negative) feedback in Earth�s climate system.

19. The albedo of sea ice is 5. (much greater than) (about the same as) (much less than) The albedo of ocean water. (table 5.1 on page 103 of text)

20. Hence, shrinkage of the Arctic sea ice cover and the attendant increase in ice-free ocean surfaces would result in 6. (greater) (about the same) (less) absorption of solar radiation during the Arctic summer.

21. This change would, in turn, lead to 7. (higher) (minimal change in) (lower) sea surface temperatures in the Arctic.

23. If Arctic Ocean surface temperatures rise as a consequence of shrinkage of sea ice cover, temperatures in the lower atmosphere over the open or ice-free arctic would also rise. (sea ice is an excellent heat insulator, greatly reducing heat flow between the water beneath the ice and the much colder air above the ice. Melting of the ice removes this insulating layer and exposes the air to heating by warmer water, where �warmer� water may be within a degree or two of 0 while air temperatures are well below freezing)

24. With higher air and water temperatures in the Arctic, we would expect the rate of melting of Arctic sea ice cover to increase leading to further 8. (warming) (cooling)

25. This is an example of 9. (positive) (negative) feedback. This ice/albedo feedback loop�

26. In this figure, �thinner ice cover� and �less snow cover� cause �more SW (solar short wave radiation) absorbed in system� because thinner ice cover and less snow cover 10. (increase) (decrease) the surface albedo.

27. Evaporation is most directly accounted for in the box entitled 11. (Thinner ice cover) (less snow cover) (increased Summer open water).

28. Less sea ice cover and higher sea surface temperatures in the Arctic Ocean would mean 12. (higher) (lower) Amounts of evaporation

29. This would lead to a 13. (drier) (more humid) lower atmosphere

30. A more humid atmosphere in the Arctic would likely increase the cloud cover. Clouds cause both cooling (by reflecting sunlight to space) and warming (by absorbing outgoing infrared radiation from Earth�s surface and radiating some of that energy downward). During the long dark polar winter, clouds would have a warming effect thus retarding the seasonal cooling. This winter time situation is an example of a 14. (positive) (negative) feedback on temperature.

31. In summer, the impact of greater cloud cover depends on the height of the clouds. Cooling would prevail with an increase in low cloud cover, thereby providing 15. (positive) (negative) feedback.

32. In summer, warming would likely accompany an increase in high cloud cover, thereby providing 16. (positive) (negative) feedback. Therefore, cloud cover provides a complex response depending on amount and height of clouds varying seasonally.

33. How would less sea ice cover in the Arctic Ocean impact the salinity of surface ocean waters? Assume that the water that evaporates from the open Arctic Ocean returns to the Arctic Ocean as precipitation or freshwater runoff. Melting of sea ice would 17. (increase) (decrease) the salinity of surface waters.

34. This change in salinity coupled with higher sea surface temperatures would 18. (increase) (decrease) the density of surface waters.

35. Changes in sea ice cover in the neighboring Greenland Sea and in the Labrador Sea south of Greenland could affect the generation of North Atlantic Deep Water (NADW) with further implications for Earth�s climate. In the North Atlantic, cold, salty NADW sinks and flows southward as part of the oceanic conveyor belt. Assuming the melting of sea ice at those latitudes where North Atlantic Deep water (NADW) is generated would produce a change in the density of surface waters, the density is likely to 19. (weaken) (strengthen) the oceanic conveyor belt. This change in strength of the oceanic conveyor belt may result in colder conditions in some regions such as Western Europe.

36. This is an example of 20. (positive) (negative) feedback considering that our analysis began with initial warming due to an enhanced greenhouse effect.

37. The wind-driven surface currents of the ocean are readily observed and have been known for some time. But the ocean is deep and the ocean�s subsurface circulation is only just now being described in detail. In the 1980�s, W. Broecker proposed that a worldwide oceanic conveyor-belt-like circulation connects all the ocean basins and transports heat energy, salt, and dissolved gases on a global scale.

38. This shows the general flow pattern of the oceanic conveyor belt. Vertical motions are due primarily to differences in water density governed by water temperature and salinity. Surface currents are wind-driven. The near-surface flow is labeled warm with directions shown by arrows. The deepwater flow is labeled cold with arrows.

39. The overall flow in the oceanic conveyor belt indicates 21. (1) (2) (3) areas of sinking motion.

40. The overall flow in the oceanic conveyor belt indicates 22. (1) (2) (3) areas of rising motion.

41. Sinking motion is shown in the 23. (northern Indian Ocean) (far North Atlantic Ocean) (north Pacific Ocean) circle all that apply.

42. Rising motion is shown in the 24. (northern Indian Ocean) (far North Atlantic Ocean) (north Pacific Ocean) circle all that apply.

43. Use Mrs. Garbiel�s picture as a guide, draw the conveyor belt circulation pattern on your paper. Use a marker to draw solid lines to represent the cold, deep conveyor circulation that extends from the North Atlantic to the Indian and North Pacific Ocean basin. Place arrowheads on the line to show direction of motion. Use the marker to draw a dashed line to represent the warm, near-surface conveyor circulation that extends from the north pacific and Indian Ocean to the north Atlantic basin.. Label cold and warm.

45. The oceanic conveyer belt has a major thermohaline component. A major driving mechanism of the conveyor belt is the sinking of water in the North Atlantic Ocean, that is , the formation of North Atlantic Deep Water (NADW). Recall as seawater freezes and ice forms, salt is excluded from the growing ice crystals making the remaining surface waters locally 25. (less)(more) saline.

46. Increased salinity and low temperatures produce seawater that is 26. (less)(more) dense and therefore more prone to sinking .

47. This shows that this dense water originating in the North Atlantic sinks to the ocean bottom and flows southward.

48. This depicts annual mean temperatures at 3000 m depth. It shows the cold water with temperatures above 2degrees C pooled at that depth in the Atlantic extended southward to nearly 27. (20 degrees)(40 degrees)(60 degrees) S. latitude.

49. South of the southern tip of Africa the temperature pattern suggests that the same water appears to flow 28. (westward)(eastward), consistent with the oceanic conveyor belt shown in this picture.

50. This depicts annual mean salinities at 3000 m depth. It shows water with salinities above 34.8 in the Atlantic extending southward to nearly 29. (20 degrees)(40 degrees)(60 degrees) S. latitude.

51. South of the southern tip of Africa the salinity pattern suggests that the same water appears to flow 30. (westward)(eastward), consistent with the oceanic conveyer belt.

52. Climate change Some scientist have hypothesized that during he early part of the Little Ice Age (around 1500) the oceanic conveyor circulation with its global hat transport was weaker or may even have ceased operating. The warm surface flow in the north Atlantic provides heat to westerly winds that help keep European temps miler than their latitude would suggest. There is a possibility that global climate change, specifically dramatic warming of Earth�s polar region, could weaken the conveyor circulation and resulting a colder climate in Europe.

53. 1. A lesson of the climate past is that __________. a. climate changes over a broad range of time scales b. climate changes in response to many forces acting together c. climate varies from place to place d. climate change may involve variations in the frequency of weather extremes

54. For information on the climate of thousands of years ago, scientists rely on __________. reconstructions based on proxy climatic data sources

55. An example of a potential proxy climatic data source is (are) __________. a. tree growth-rings b. glacial ice cores c. deep-sea sediment cores d. pollen

56. Much of what is known about the large-scale climatic fluctuations of the Pleistocene Ice Age is based on analysis of __________. deep-sea sediment cores

57. The ocean inhibits wild fluctuations in climate because the ocean __________. has a great thermal inertia

58. In addition to instrument measurements, climate is documented by analysis of __________. a. bedrock and fossil types b. ancient pollen c. economic data d. ship logs and diaries.

59. Deep-sea sediment cores can provide a climate chronology going back as far as ___________ years. millions of

60. Through __________ analysis, scientists can reconstruct past variations in glacial ice volume from deep-sea sediment cores. oxygen isotope

61. Scientists can distinguish between cold and warm episodes in the climatic past through analysis of __________ in microscopic shells contained in deep-sea sediment cores. *a. oxygen isotopes

62. Oxygen isotope analyses of both deep-sea cores and ice cores (from the Greenland ice sheet) show that the Pleistocene ___________. consisted of numerous glacial climatic episodes

63. The technique of reconstructing past climates from pollen profiles assumes that __________. a. pollen is of local origin b. climate is the principal control of vegetation type c. pollen resists decomposition

64. Ice cores for climate reconstruction __________. a. may span hundreds of thousands of years b. are extracted from glacial ice c. provide information on changes in greenhouse gas concentration d. can provide evidence of past volcanic eruptions

65. On geologic time scales of millions of years, climate is influenced by __________. a. plate tectonics and continental drift b. mountain ranges rising and eroding away c. changes in the geographical extent of the ocean d. meteorite impacts

66. About 570 million years ago, the transition between the Precambrian and Paleozoic Eons was marked by __________. dramatic global cooling with the oceans freezing to a depth of perhaps 1000 m

67. Each interglacial climate episode during the Pleistocene lasted about __________. 10,000 years

68. The Holocene or Recent Epoch __________. *a. has been mostly an interglacial climate episode

69. Polar amplification refers to __________. an increase in the magnitude of climatic change with increasing latitude

70. The Younger Dryas __________. was a relatively cold episode that occurred about 10,000 to 11,000 years ago

71. The Vikings reached North America during the __________. *a. Medieval warm period

72. Reliable instrument-based temperature records began about __________. 1880 The trend in instrument-derived temperatures from the 1800s to the present shows a general __________. increase in both land and ocean temperatures

73. Temperature records for Earth as a whole suggest __________ over the last century. a warming trend

74. The integrity of the global mean temperature record has been questioned by some because of the potential effects of __________. a. warming due to urbanization b. changes in location and exposure of instruments at long-term sites c. ongoing improvements in the sophistication and reliability of instruments d. gaps in monitoring networks, especially over the ocean

75. The long-term climate record suggests all of the following except that __________. a. climate is variable over a wide range of temporal and spatial scales *b. in the long term, climate is predictable c. climate change tends to be abrupt rather than gradual d. climate change affects society e. climate change is geographically non-uniform in direction and magnitude

76. A natural phenomenon that typically influences climate over a period of one to two years is (are) __________. a. mountain building b. Milankovitch cycles *c. sulfur-rich violent volcanic eruptions d. significant change in the area of the ocean surface e. All of the above are correct.

77. With global radiative equilibrium the solar energy input into the Earth-atmosphere system __________ the flux of infrared radiation from Earth to space. *a. balances

78. A factor that can alter Earth�s global radiative equilibrium and thereby change climate is __________. a. the sun�s energy output b. sulfur-rich volcanic eruptions c. cloud cover d. Earth�s surface properties

79. Evidence of climate change due to continental drift includes __________. a. glacial deposits in tropical deserts b. fossilized tropical plants in Greenland c. coal in Antarctica d. fossilized coral in Wisconsin

80. Sea floor spreading causes large-scale climate change by __________. a. opening and closing seas and ocean basins b. altering ocean circulation patterns c. changing ocean heat transport

81. Variability in the input of solar radiation into the Earth-atmosphere system can be caused by __________. a. sun spots b. changes in Earth�s orbit about the sun c. changes in the amount of interplanetary dust between sun and Earth

82. Regular long-term variations in Earth�s axial tilt and orbit around the sun are known as __________ cycles. a. Maunder *b. Milankovitch

83. Milankovitch cycles are regular long-term variations in Earth�s __________. a. axial tilt b. orbital eccentricity about the sun c. precession

84. Milankovitch cycles operate over all of the following periods with the exception of __________. 10 million years

85. Milankovitch cycles are a principle cause of __________. *c. large-scale fluctuations of glacial ice on Earth over the past 1.7 million years

86. Explosive volcanic eruptions are likely to impact climate only if their emissions are rich in __________. *b. sulfur dioxide

87. . The human activity most likely to impact climate on a global scale is __________. combustion of fossil fuels

88. Earth�s greenhouse effect is principally due to the presence of __________ in the atmosphere. a. carbon dioxide b. methane *c. water vapor d. nitrogen e. oxygen

89. The increase in atmospheric carbon dioxide concentration since the Industrial Revolution was primarily due to __________. *a. the burning of fossil fuels

90. Which one of the following statements is not true? a. Cold ocean water can absorb more carbon dioxide than warm ocean water. b. Carbon dioxide is taken up in the ocean by photosynthetic organisms. c. The ocean is a major reservoir in the global carbon cycle. *d. The deep-ocean conveyor belt typically sequesters carbon for only a decade or so.

91. Which of the following is likely to be a consequence of global warming? a. rise in ocean level b. rise in sea-surface temperature c. melting sea ice

92. The rise in sea level in response to global warming is caused by all of the following with the exception of ___________. *a. melting sea ice b. melting mountain glaciers c. thermal expansion of sea water d. melting ice sheet on Greenland

93. Worldwide, mountain glaciers are predominantly __________. *a. shrinking

94. With a warmer climate, Great Lakes water levels would most likely __________. fall

95. Melting sea ice cover in the Arctic Ocean is likely to lead to ___________. *a. an accelerated rate of melting of sea ice

96. As the sea-ice cover of the Arctic Ocean shrinks in area, the albedo of the surface __________. a. increases *b. decreases

97. The thermal properties of the ocean __________ global-scale changes in climate. a. amplify *b. dampen

98. Deep-sea sediment cores __________. a. record past changes in climate b. provide evidence of the Milankovitch cycles c. confirm that climate tends to change abruptly

99. Warming in the high latitude Arctic could lead to the ocean conveyor belt ___________. *a. slowing or stopping causing cooling