Sea Level Change in a Warming World: An Update. Jerry X Mitrovica Department of Earth & Planetary Sciences Harvard University

Transcription

1 Sea Level Change in a Warming World: An Update Jerry X Mitrovica Department of Earth & Planetary Sciences Harvard University

2 Sea Level Change in a Warming World: An Update Part 1: The Greenhouse Effect & Global Warming

3 Part 5: Critical Events Testing the Earth s Resilience The Underlying Problem: The Greenhouse Effect & Global Warming Earth s Radiation Budget

4 Part 5: Critical Events Testing the Earth s Resilience The Underlying Problem: The Greenhouse Effect & Global Warming Earth s Radiation Budget Energy absorbed by land/water is re-emitted and some of this energy is trapped by greenhouse gases

5 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Natural Greenhouse Effect. If the Earth had no atmosphere (and no greenhouse gases) our mean surface temperature would be -18 C

6 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Natural Greenhouse Effect. If the Earth had no atmosphere (and no greenhouse gases) our mean surface temperature would be -18 C Actual mean surface temperature is +15 C

7 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Greenhouse Effect for an Earth out of Balance Charles David Keeling Curve

8 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Greenhouse Effect for an Earth out of Balance Spring-summer photosynthesis rises Fall-winter photosynthesis falls and soil bacteria respire Seasonal cycle

9 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Greenhouse Effect for an Earth out of Balance

10 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Greenhouse Effect for an Earth out of Balance Thought to be due to increase in sulfate aerosols due to increase in coal and diesel fuel burning

11 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Greenhouse Effect for an Earth out of Balance What is causing this? China coal burning? Deep ocean heat uptake?

12 Charles David Keeling Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Greenhouse Effect for an Earth out of Balance If burning fossil fuels increases CO 2, what happens to levels of free oxygen?

13 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming The Greenhouse Effect for an Earth out of Balance Two possibilities: Ocean Uptake Diffusion of some CO 2 into ocean (sink) Land Uptake CO 2 fertilization leads to growth of forests and rise of photosynthesis (sink)

14 Part The Underlying 5: Critical Problem: Events The Testing Greenhouse the Effect Earth s & Global Resilience Warming Why is CO2 such a problematic greenhouse gas? Lets consider an ancient event in Earth history the Paleocene-Eocene Thermal Maximum: Sharp increase In temperature

15 Sea Level Change in a Warming World: An Update Part 2: An Update on Science of Sea Level Change

16 Part An Update 5: Critical on the Events Science of Sea Testing Level the Change Earth s Resilience The Causes of Modern Sea Level Change

17 Part An Update 5: Critical on the Events Science of Sea Testing Level the Change Earth s Resilience The Present Day Signal of the Ice Age 1-3 mm/yr sea level rise NEAR FIELD

18 Part An Update 5: Critical on the Events Science of Sea Testing Level the Change Earth s Resilience Tide Gauge Records Satellite Altimetry Modern Sea Level Records

19 Part An Update 5: Critical on the Events Science of Sea Testing Level the Change Earth s Resilience Tide Gauge Records Modern Sea Level Records

20 Part An Update 5: Critical on the Events Science of Sea Testing Level the Change Earth s Resilience Tide Gauges: Some limitations Tide Gauge Records Dunkirk Mombasa

21 Global mean sea level (m Global mean sea level (m Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Reconstructed 20 th Century Global Mean Sea Level: New Estimate = ~1.2mm/yr Rate (mm/yr) Rate (mm/yr) Rate (m Rate (m KS ± ± GPR KS ± ± Church GPR and White ± ± Church Jevrejeva and et White al ± ± Jevrejeva et al Old Estimates = ~ mm/yr Calendar year Calendar year Hay et al. [Nature, 2015)

22 Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience IPCC AR5: The Budget of 20 th Century GMSL

23 Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Reconstructed 20 th Century Global Mean Sea Level: New Estimate = ~1.2mm/yr Old Estimates = ~ mm/yr 1. It s not going to get worse 2. It s been rising for millennia 3. It varies from place to place Hay et al. [Nature, 2015)

24 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Its not going to get worse Satellite Altimetry

25 15-yr 15-yr rate Rate count Count Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Its not going to get worse 15 Year Running Averages 15-yr 15-yr sea-level Sea-Level Rate (mm/yr) rate

26 Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Reconstructed 20 th Century Global Mean Sea Level: New Estimate = ~1.2mm/yr Old Estimates = ~ mm/yr 1. It s not going to get worse 2. It s been rising for millennia 3. It varies from place to place Hay et al. [Nature, 2015)

27 Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Quaternary Science Reviews 21 (2002) On the origin of late Holocene sea-level highstands within equatorial ocean basins J.X. M itrovica a, *, G.A. M ilne b a Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ont., Canada M 5S 1A7 b Department of Geological Sciences, University of Durham, Durham DH1 3LE, UK Received 27 February 2002; accepted 3 June 2002 Malden Island Abstract Late Holocene sea-level highstands of amplitude B 3 m are endemic to equatorial ocean basins. These highstands imply an ongoing and moderate, sub-mm/yr, sea-level fall in the far field of the Late Pleistocene ice cover that has long been linked to the

28 Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Salt Marshes: High Resolution Indicators of Sea Level Change Vegetation, microfossils and sediment each provide an indicative range on sea level MTL mean tide level MHW - high water HAT highest astronomical tide Engelhart & Horton (2012)

29 Sea Level (m) Part 5: Critical Events Testing the Earth s Resilience Part An Global Geological Update 5: Mean Critical on Records Sea the Events Science Level - II Rise of Sea Testing Level the Change Earth s Resilience Salt Marshes: High Resolution Indicators of Sea Level Change Kemp et al. (2012)

30 Late Republic begins Julius Caesar Assassinated Augustus first emperor Augustus dies Commodus decline begins Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Roman Republic Roman Empire 300 BC 200 BC 100 BC AD 200 AD Fish tank (piscinae) construction PAX ROMANA Archeological Constraints: Roman Fish Tanks

31 Sea Level (cm) Relative to 1900AD Part 5: Critical Events Testing the Earth s Resilience Statistical An Global Update Mean Analysis on Sea the Science Level of Available Rise of Sea Records Level Change Estimate of global mean sea level change based on geological and archeological records: Years (AD)

32 Sea Level (cm) Relative to 1900AD Part 5: Critical Events Testing the Earth s Resilience Statistical An Global Update Mean Analysis on Sea the Science Level of Available Rise of Sea Records Level Change Estimate of global mean sea level change based on geological and archeological records: Variation over 2000 years is less than the sea level rise since 1900AD Years (AD)

33 Part 5: Critical Events Testing the Earth s Resilience Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Reconstructed 20 th Century Global Mean Sea Level: New Estimate = ~1.2mm/yr Old Estimates = ~ mm/yr 1. It s not going to get worse 2. It s been rising for millennia 3. It varies from place to place Hay et al. [Nature, 2015)

34 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience What would happen to sea level if the Greenland Ice Sheet collapsed?

35 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience What would happen to sea level if the Greenland Ice Sheet collapsed? The bathtub???

36 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience What would happen to sea level if the Greenland Ice Sheet collapsed?

37 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience What would happen to sea level if the Greenland Ice Sheet collapsed? Normalized Sea Level Change Sea Level Fingerprints of Rapid Ice Sheet Melting

38 Part 5: Critical Events Testing the Earth s Resilience Part An Sea Global Update Level 5: Mean Critical on Fingerprints Sea the Events Science Level Rise of Rapid Sea Testing Level Ice the Sheet Change Earth s Melting Resilience Normalized Sea Level Change

39 Part 5: Critical Events Testing the Earth s Resilience An Sea Global Update Level Mean on Fingerprints Sea the Science Level Rise of Rapid Sea Level Ice Sheet Change Melting

40 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Sea Level Projections to the End of the 21 st Century???

41 Part 5: Critical Events Testing the Earth s Resilience Part An Sea Global Update Level 5: Mean Critical on Fingerprints Sea the Events Science Level Rise of Rapid Sea Testing Level Ice the Sheet Change Earth s Melting Resilience Normalized Sea Level Change

42 Part An Sea Global Update Level 5: Mean Critical on Fingerprints Sea the Events Science Level Rise of Rapid Sea Testing Level Ice the Sheet Change Earth s Melting Resilience Hyannis Hyannis A new tool for coastal planners 0.05

43 Part An Sea Global Update Level 5: Mean Critical on Fingerprints Sea the Events Science Level Rise of Rapid Sea Testing Level Ice the Sheet Change Earth s Melting Resilience GRACE Satellite Gravity Mission

44 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience The Causes of Modern Sea Level Change

45 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Argo Floats: Measure Temperature and Salinity in the Upper 2000 m

46 Part An Global Update 5: Mean Critical on Sea the Events Science Level Rise of Sea Testing Level the Change Earth s Resilience Some Conclusions Global mean sea level rise was relatively constant in the last 3000 years, it began to rise at the end of the 19 th century, and is now accelerating. Projections suggest that GMSL will increase ~1 m over the current century (but it may be significantly higher). Sea level changes show dramatic geographic variability and coastal planning must take this into account Tools are being developed to provide planners the ability to track and project sea level changes at specific sites as more and more observations come online (more to come)