OceanMOOC | 1.4 | Human influence on the Ocean

Summary

The video explores how human activities, particularly the burning of fossil fuels, have significantly impacted the oceans, marking the Anthropocene era. Key issues include global warming due to CO2 emissions, which heats land and ocean surfaces and alters ocean currents, leading to regional warming variations. The ocean absorbs most of the greenhouse gas-induced heat, causing thermal expansion and melting ice, contributing to rising sea levels. Additionally, the oceans absorb CO2, resulting in acidification and negatively affecting marine biodiversity, especially coral reefs. Future projections suggest escalating temperature increases, continued sea level rise, and further biodiversity damage if climate actions are not taken.

Highlights

• Human influence on oceans is comparable to natural forces, marking the Anthropocene era. 🌱
• Burning fossil fuels emits CO2, a significant greenhouse gas contributing to global warming. 🌞
• Oceans act as a carbon sink, absorbing 25% of CO2 emissions, leading to acidification. 🌊
• Ocean warming affects marine life, with corals unable to survive beyond a 1.5°C rise. 🐠
• Sea level rise is primarily due to thermal expansion and melting ice, not uniform across regions. 📈

Key Takeaways

• Human activities, especially fossil fuel burning, heavily influence ocean conditions. 🌍
• Oceans absorb 90% of the heat generated by greenhouse gases, leading to thermal expansion and sea level rise. 🌊
• Regional variations in sea level rise are due to changing wind patterns and ocean currents. 🌀
• Ocean acidification from CO2 uptake poses a threat to marine biodiversity, especially calcifying organisms like corals. 🐠
• Without significant climate protection, the oceans will continue to warm, acidity levels will rise, and biodiversity could dramatically decline. 🔥

Overview

Human activities, particularly the burning of fossil fuels, have intensified their influence on the oceans, marking a shift to what some call the Anthropocene era. The primary issue stems from CO2 emissions, a major greenhouse gas responsible for warming the Earth's atmosphere and oceans. The resulting temperature rise is not uniform, as regions like the Arctic warm faster than others, impacting ocean currents and ecosystems.

The oceans absorb about 90% of the additional energy from greenhouse gases, causing significant warming that affects both sea levels and marine life. This warming leads to thermal expansion, leading to sea level rise, and contributes to the melting of polar ice, further elevating sea levels. These changes are not evenly distributed, with some regions experiencing more significant effects than others.

Additionally, the oceans help mitigate climate change by absorbing CO2, but this leads to acidification, threatening marine biodiversity. The decrease in carbonate ions impairs calcifying organisms, such as corals, impacting their ability to construct their shells and skeletons. As climate change continues without effective interventions, these issues are poised to worsen, further endangering marine ecosystems and global biodiversity.

Chapters

• 00:00 - 00:30: Introduction to Human Influence on Oceans The chapter discusses the increasing human influence on the oceans, highlighting the variability within oceanic systems. The term "Anthropocene" is introduced, suggesting a new era characterized by significant human impact.
• 00:30 - 01:40: Impact of Fossil Fuels on Global Warming The chapter discusses the significant impact of fossil fuels on global warming, particularly focusing on how burning coal, oil, and natural gas releases large amounts of carbon dioxide (CO2) into the atmosphere. CO2 is identified as a greenhouse gas that plays a key role in affecting the earth's climate system, including the ocean, in a manner comparable to natural environmental forces. The chapter emphasizes the problem of energy production through fossil fuel combustion and its contribution to global CO2 levels.
• 01:40 - 03:10: Effect of CO2 on Atmosphere and Oceans The chapter discusses the effect of CO2 on the atmosphere and oceans. It explains that CO2 is a greenhouse gas, contributing to global warming and climate change. A significant portion of emitted CO2 remains in the atmosphere for decades, affecting climate patterns. Additionally, about a quarter of the CO2 is absorbed by vegetation, while another quarter is absorbed by the oceans, which has various implications for marine life and oceanic conditions.
• 03:10 - 05:50: Ocean Warming and Sea Level Rise This chapter discusses the impact of global warming on ocean temperatures and sea levels. It explains how global warming results in the warming of both land and ocean areas. The text highlights that ocean warming, which can be measured down to several hundred meters, is a significant consequence of anthropogenic climate change, emphasizing the extensive volume of water being warmed.
• 05:50 - 10:00: Role of Ice Melt in Sea Level Rise The chapter discusses the impact of ice melt on sea level rise, emphasizing how melting ice contributes to changing ocean currents. These altered currents result in regional variations in warming patterns, indicating that different areas are not experiencing warming in a uniform manner over the past fifty years.
• 10:00 - 13:50: Consequences of Global Warming on Marine Life The chapter discusses the regional variations in global warming and its impact on marine life. While some regions on Earth have not experienced significant warming, others, like the Arctic, have seen temperatures rise considerably above the global average. The text emphasizes that about 90% of the extra energy generated due to increased greenhouse gases is a significant factor in these changes.
• 13:50 - 18:30: Future Projections and Climate Experimentation This chapter discusses the role of the oceans in absorbing heat, leading to thermal expansion and sea level rise. It details that since 1900, the global average sea level has risen by approximately 20 centimeters, with oceans playing a significant role in capturing heat.

OceanMOOC | 1.4 | Human influence on the Ocean Transcription

• 00:00 - 00:30 We have learned that there is a lot of variability in the oceans but during the recent decades, the human influence on the oceans becomes stronger and stronger. And some people talk already about the Anthropocene, the new era we are entering where humans have actually
• 00:30 - 01:00 impact on the earth system and especially on the ocean that is comparable to the impact of the natural forcings. Now the main problem here is that we produce energy by burning fossil fuels, so by burning coal, by burning oil and by burning natural gas. And if we do that, we produce vast amounts of carbon dioxide, CO2, and CO2 is known to be a greenhouse
• 01:00 - 01:30 gas. So it warms the atmosphere, it leads to global warming. So some part of the CO2 that we emit into the atmosphere remains there for many, many decades. But another part is taken up by the vegetation so by the plants. That’s about a quarter, and another quarter is taken up by the oceans. Now let us start with the 50%
• 01:30 - 02:00 that remains in the atmosphere because that produces global warming and global warming means not only that the land area is warm but also that the oceans warm. And we can actually measure the ocean warming down to several hundred meters, that’s a big volume actually that warms in response to anthropogenic climate change as we say.
• 02:00 - 02:30 Now this also leads to changing ocean currents and the changing ocean currents lead to regional variations in the warming pattern so if we look at the warming pattern say during the recent fifty years or so we don’t see you know that all areas warmed in the same manner
• 02:30 - 03:00 but we see a lot of regional variations and actually there are a few regions on this planet which haven’t really warmed at all, while other regions like the arctic has warmed much more than the global average temperature. So about 90%...90% of the additional energy that has been produced by the increase of greenhouse gases in the atmosphere has wound
• 03:00 - 03:30 up in the ocean. So the oceans have taken up heat, vast amounts of heat. If this happens, the water column expands and this leads to sea level rise and we have measured a sea level rise since 1900 on the order of 20 centimeters in the global average. About ten centimeters
• 03:30 - 04:00 arise from the thermal expansion effect, okay? So by the...from the fact that the ocean has taken up heat and expands. Now global warming also leads to ice melt and we have basically two types of ice that impact the ocean. One is sea ice. If you look into the arctic, we see that the sea ice has retreated very quickly during the recent decades, satellite measurements
• 04:00 - 04:30 have started around 1978 and since then the sea ice, the Arctic sea ice has retreated by approximately 30%, okay? This does not affect sea level because the ice is already floating in the ocean, however if land ice melts, and this is happening, ice on Greenland for instance, then the melt water will wind up in the ocean and this will
• 04:30 - 05:00 cause additional sea level rise. And the other 10 centimeters of sea level rise that we have measured since 1900 actually comes from the ice melt, so from the melt of the mountain glaciers but also increasingly from the melt of Greenland and the Antarctic ice sheet and for many decades, it was actually the thermal expansion that dominated the sea level rise
• 05:00 - 05:30 but now during the last years it is already the ice melt, the land ice melt, that dominates sea level rise and contributes more than half for the current rise and this is expected to further accelerate. But also sea level rise is not uniform. We see a lot of regional variations during the last decades, the region that has experience...experienced the largest sea level rise is the western tropical Pacific. There, sea level has risen
• 05:30 - 06:00 about three times faster than the global average. On the other side of the tropical Pacific, sea level hasn’t really risen and the reason for this major difference in sea level rise across the tropical Pacific is the change in the winds. So the winds across the Pacific equator have intensified. This piled up amount of warm water in the west, okay, that caused
• 06:00 - 06:30 sea level to rise okay, while this warm water actually is missing in the east and this is why there isn’t hardly any sea level rise during the last decades in the eastern tropical Pacific. Now we have seen there are two consequences of global warming. One is the warming of the ocean and...and this by itself is a problem. Corals for instance can’t really survive if there will be a sustained warming in excess
• 06:30 - 07:00 of say 1.5 degrees Celsius so the warming by itself is a major threat to the marine ecosystems. We have seen that sea level has risen and this will continue but there is another problem that we refer to as the other climate problem, and this is that the oceans not only take up heat, but they also take up carbon dioxide, CO2. This must automatically...automatically
• 07:00 - 07:30 lead to ocean acidification. So the oceans become more acidic if they take up carbon dioxide so that’s a fundamental chemical reaction that we can’t avoid. So as long as we emit carbon dioxide into the atmosphere, a certainly fraction of that will always go into the ocean and this will lead to acidification. This also can be very dangerous to the marine
• 07:30 - 08:00 ecosystems because on the one hand if the water becomes more acidic, this can be harmful to many marine species but on the other hand, the uptake of carbon by the ocean also leads
• 08:00 - 08:30 to diminishing carbonate concentrations in the oceans, and this is basically what calcifying organisms as we say need to build their shells, their skeletons and so on. Corals for instance, they need to build skeletons and you know if the carbonate isn’t available anymore, then they can’t do it and they need to produce, use more energy and so on so in the end they
• 08:30 - 09:00 will probably no longer be able to build the structures they desperately need and this then in turn will cause a loss of biodiversity and so on. So how will the ocean state evolve in the future and one of the great oceanographers,
• 09:00 - 09:30 Roger Revelle once said that we are carrying out a giant geophysical experiment with our earth system and I would like to stress this because there are uncertainties, we can’t really compute everything, our models are not perfect, our data is not perfect and certainly not enough but if we investigate what the models predict, then we see that on the one
• 09:30 - 10:00 hand the temperature of the planet and also the temperature of the oceans, will continue to rise. If we will experience something like an accelerating climate change, okay if there won’t be any climate protection, then we will have an additional warming in the global
• 10:00 - 10:30 average of four or five, maybe six degrees this will be... will lead to a complete loss of tropical corals, sea level will rise by an additional one meter by the end of the century but you know with strong regional variations. But how exactly these regional variations will be, this is really hard to predict because you would have to predict also the change in ocean circulation and finally, acidification will continue.
• 10:30 - 11:00 We will in the worst case scenario, have PH values by which we measure the acidity of the sea water well below a value of 8 and well...we believe that if this really happens, many marine ecosystems will be endangered and biodiversity will dramatically decline
• 11:00 - 11:30 in response to this huge acidification and this will be an acidification that we haven’t experienced for many, many million years and it will be at least unprecedented in man’s history.