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The significance of vertical land movements at convergent plate boundaries in probabilistic sea-level projections for AR6 scenarios: The New Zealand case.
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  • Tim Naish,
  • Richard H. Levy,
  • Ian James Hamling,
  • Gregory Garner,
  • Sigrún Hreinsdóttir,
  • Robert E Kopp,
  • Nicholas R. Golledge,
  • Robert Bell,
  • Ryan Paulik,
  • Judy Lawrence,
  • Paul H. Denys,
  • Tasman Gillies,
  • Shannon Bengston,
  • Kate Clark,
  • Daniel King,
  • Nicola Jane Litchfield,
  • Laura Wallace,
  • Rewi Newnham
Tim Naish
Victoria University of Wellington

Corresponding Author:[email protected]

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Richard H. Levy
Geological and Nuclear Sciences - Te Pu Ao
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Ian James Hamling
GNS Science
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Gregory Garner
Rutgers University
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Sigrún Hreinsdóttir
GNS Science
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Robert E Kopp
Rutgers University
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Nicholas R. Golledge
Victoria University of Wellington
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Robert Bell
Bell Adapt
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Ryan Paulik
National Institute of Water and Atmospheric Research
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Judy Lawrence
New Zealand Climate Change Research Institute, Victoria University of Wellington
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Paul H. Denys
University of Otago
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Tasman Gillies
Toha-Takiwa Lts
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Shannon Bengston
GNS Science, 1 Fairway Drive, Avalon,
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Kate Clark
GNS Science
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Daniel King
1Antarctic Research Centre, Victoria University of Wellington
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Nicola Jane Litchfield
GNS Science
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Laura Wallace
GNS Science
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Rewi Newnham
Victoria University of Wellington, PO Box, 600, Wellington
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Abstract

Anticipating and managing the impacts of sea-level rise for nations astride active tectonic margins requires rates of sea surface elevation change in relation to coastal land elevation to be understood. Vertical land motion (VLM) can either exacerbate or reduce sea-level changes with impacts varying significantly along a coastline. Determining rate, pattern, and variability of VLM near coasts leads to a direct improvement of location-specific relative sea level (RSL) estimates. Here, we utilise vertical velocity field from interferometric synthetic aperture radar (InSAR) data, calibrated with campaign and continuous Global Navigation Satellite System (GNSS), to determine the VLM for the entire coastline of New Zealand. Guided by existing knowledge of the seismic cycle, the VLM data infer long-term, interseismic rates of land surface deformation. We build probabilistic RSL projections using the Framework for Assessing Changes to Sea-level (FACTS) from IPCC Assessment Report 6 and ingest local VLM data to produce RSL projections at 7435 sites, thereby enhancing spatial coverage that was previously limited to tide gauges. We present ensembles of probability distributions of RSL for medium confidence climatic processes for each scenario to 2150 and low confidence processes to 2300. For regions where land subsidence is occurring at rates >2mm yr-1 VLM makes a significant contribution to RSL projections for all scenarios out 2150. Beyond 2150, for higher emissions scenarios, the land ice contribution to global sea level dominates. We discuss the planning implications of RSL projections, where timing of threshold exceedance for coastal inundation can be brought forward by decades.