Past, present and future

Transcription

1 Southern New Jersey and Delaware sea levels: Past, present and future Benjamin P. Horton Sea Level Research Department of Marine and Coastal Science Rutgers University

2 DRIVERS OF SEA-LEVEL CHANGE Relative Sea Level = Eustasy + Isostasy + Tectonic + Local

3 (1) Sea levels of the past Rutgers University Marine Field Station

4 Salt marshes and sea level Distinctive pattern of floral zonation (tolerance of frequency and duration of inundation) Sedimentary sequences are archives of sea-level change

5 HOW DO WE RECONSTRUCT PAST SEA-LEVELS? Location Age RSL: it is necessary to establish the a) Elevation of sample b) relationship of the sample to a tide level (indicative meaning)

6 MODERN ANALOGUES We define the relationship between a sea-level indicator and a tide level in the modern environment

7 FOSSIL ENVIRONMENT Sea Level is calculated by subtracting the reference water level from the elevation of the dated sample RSL i = E i - RWL i

8 EXAMPLE OF AN INDEX POINT

9 CALCULATION OF SEA LEVEL

10 THE INFLUENCE OF TIDAL RANGE If the tidal range has not remained constant through time, sea-level chronologies based upon tide-level indicators will differ from the true sea-level curve

11 RATIOS OF TIDAL RANGES TO THEIR PRESENT DAY VALUES

12 CORRECTION FOR TIDAL RANGE Paleotidal range was relatively constant during the mid and late Holocene, but rapidly increased between 9 and 8 ka, leading to an underestimation of RSL by ~0.5 m (Horton et al., JQS, 2013)

13 THE INFLUENCE OF COMPACTION Compaction will lower index points from their original elevation and will lead to an overestimate of the rate of RSL rise

14 CORRECTING FOR COMPACTION New Jersey Horton et al., 2013 JQS

15 US ATLANTIC COAST SEA-LEVEL DATABASE

16 USA HOLOCENE SEA LEVEL Atlantic Ocean 5 7 Engelhart & Horton 2012, QSR

17 10,000 years ago

18 9,000 years ago

19 8,000 years ago

20 7,000 years ago

21 6,000 years ago

22 5,000 years ago

23 4,000 years ago

24 3,000 years ago

25 2,000 years ago

26 1,000 years ago

27 Present day

28 USA <1.0 mm/yr LATE HOLOCENE SEA LEVEL mm/yr Atlantic Ocean <1.0 mm/yr Engelhart et al 2011, Geology 0.6

29 RATE OF LATE HOLOCENE RELATIVE SEA- LEVEL RISE ALONG THE U.S. ATLANTIC COAST

30 RATE SEA- LEVEL RISE: Late Holocene vs. Modern Era

31 (2) SEA LEVELS OF THE PRESENT Andy Kemp and Simon Engelhart (now Assist Profs)

32 STUDY AREAS ALONG THE US ATLANTIC COAST

33 Bridge the gap between geological and instrumental records

34 EXAMPLE FROM NEW JERSEY AND DELAWARE

35 QUANTITATIVE MODELS TO RECONSTRUCT SEA LEVEL Sampling stations are placed along an elevational gradient Foraminifera: Strong environmental preferences with narrow elevational zones Abundant = quantitative Cheap, but time consuming. Andy counted 46,324 foraminfera!

36 Great Marsh, Delaware

37

38 Fossil foraminifera (Y 0 ) are observed in sedimentary archives. The transfer function estimates the elevation (X 0 ) with respect to sea level a decimeter precision

39 FOSSIL FORAMINIFERA OF CAPE MAY

40 COMPOSITE CHRONOLOGIES Plateau in the calibration curve for the last ~350 years Pollution markers of known age are region specific

41 Age of any sample estimated with uncertainty Decadal resolution

42 RELATIVE SEA LEVEL IN NEW JERSEY

43 RATES OF RELATIVE SEA LEVEL IN NEW JERSEY

44 COMPARISION OF THE PROXY VS. TIDE GAUGE

45 GIA-adjusted sea level Rate of sea-level rise Connecticut New Jersey North Carolina Florida

46 Our PNAS paper was referenced by President Obama in his 2015 State of the Union Address at the United States Capitol on January 20, 2015

47 REGIONAL SEA-LEVEL CHANGE

48 REGIONAL VARIABILITY OF SEA LEVEL

49 STATIC EQUILIBRIUM As the mass of an ice sheet shrinks, sealevel rise is greater in areas geographically distal

50 OCEAN DYNAMIC EFFECTS A weaker Gulf Stream as a result of a fading Atlantic Meridional Overturning Circulation (AMOC), would cause a sea-level rise ( hotspot ) in northeastern North America relative to the southeastern United States

51 REGIONAL SEA-LEVEL CHANGE Static equilibrium: would required a GIS mass loss of nearly 2 m sea-level equivalent Ocean dynamics: consistent with an intensification of the AMOC (or southward migration of the ITCZ)

52 COMMON ERA SEA LEVEL DATABASE (Horton et al., 2016)

53 GLOBAL MEAN SEA LEVEL A significant sea level acceleration beginning in the 19th century yielded a 20th century rise that is extremely likely (probability P >0.95) faster than during any of the previous 27 centuries.

54

55 (2) Sea levels of the future

56 GLOBAL MEAN SEA LEVEL PROJECTIONS Horton et al., 2014

57 ESTIMATES OF GLOBAL MEAN SEA LEVEL FROM SEMI-EMPIRICAL MODELS Horton et al., 2014

58 ASSESSMENTS OF GLOBAL MEAN SEA-LEVEL Horton et al., 2014

59 SEMI-EMPIRICAL MODELS OF SEA-LEVEL RISE USING PROXY DATA

60 COUNTERFACTUAL OF SEA-LEVEL RISE Over 50% of SLR due to human activities

61 SEMI-EMPIRICAL MODELS VS IPCC 5AR Reconcile differences between IPCC projections and semi-empirical models

62

63 REGIONAL SEA-LEVEL RISE: DELAWARE Kopp, Horton, et al. (2015)

64 SEA-LEVEL RISE FOR LEWES, DE Year RCP4.5 RCP8.5 Quantile 50% 17-83% 5-95% 50% 17-83% 5-95%

65 SEA-LEVEL RISE FOR LEWES, DE

66 INDIVIDUAL COMPONENTS OF SEA-LEVEL RISE FOR LEWES, DE SLR at Lewes by 2100 RCP8.5 50% 17-83% 5-95% Antarctic Ice Sheet Greenland Ice Sheet Ocean (thermal + circulation changes) Glaciers and Ice Caps Land Water Storage Background (including GIA) The largest contribution and uncertainty is the oceans although the Antarctic ice could play a significant role later in the 21 st century

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68 SUMMARY High resolution records derived from salt-marsh indicators

69 SUMMARY Along the mid Atlantic coastlines multi-century patterns of sea-level variability consistent with ocean dynamics

70 SUMMARY Global mean sea level of the Common Era reveals unprecedented rise beginning in late 19th century

71 SUMMARY Probabilistic projections of sea-level for Delaware with a 50 th percentile rise of 99 cm by 2100