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Decadal sea level variations in the North Atlantic and Arctic Oceans Kristine S. Madsen and Torben Schmith Centre for Ocean and Ice, Danish Meteorological Institute. Overview. Introduction Tide gauge observations A composite record for the Nordic Seas

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Decadal sea level variations in the North Atlantic and Arctic OceansKristine S. Madsen and Torben SchmithCentre for Ocean and Ice, Danish Meteorological Institute

overview
Overview

Introduction

Tide gauge observations

  • A composite record for the Nordic Seas
  • The observed sea level signal of the 1940’s

Model analysis

  • Characteristic time scales of the North Atlantic and the Arctic Oceans
  • Climate model sea level and the 1940’s

Summary

introduction
Introduction
  • Global sea level changes are overlaid by regional variability
  • Here, we focus on multidecadal variability in the North Atlantic and Arctic sea level
  • Recent multidecadal variability in the North Atlantic area
    • warming of the 1940s
    • warming of recent decades
    • intervening cool period
tide gauge observations
Tide gauge observations

Monthly RLR data from PSMSL

  • All records north of 60N except Baltic with at least 50% available data during 1940-1949: 5 Norwegian and 2 Russian
  • 5 European stations
  • 5 NE American stations

b

c

a

norwegian russian composite record monthly data
Norwegian/Russian composite record – monthly data
  • Monthly data used
  • 1925-2010

Units: m

norwegian russian composite record annual mean
Norwegian/Russian composite record – annual mean
  • Annual mean if at least 9 month available
  • Mean and linear trend removed to remove land rise effects

Units: m

norwegian russian composite record
Norwegian/Russian composite record
  • Records now comparable

Units: m

norwegian russian composite record1
Norwegian/Russian composite record
  • Records now comparable
  • Ensemble mean

Units: m

norwegian russian composite record running mean
Norwegian/Russian composite record – running mean
  • Running mean
    • 10 years (blue)
    • 19 years (green)

Units: m

the ec earth model
The EC-Earth model

Fully coupled GCM

Two sets of runs:

  • 600 years control run (pre-industrial forcing)
  • Ensemble of historic runs 1850 – now

Atmosphere GCM: IFS

Land: IFS H-tessel

Vegetation:

Orchideel/LPJ

Coupler:

OASIS3

ATM Chemistry and

aerosols: TM5

Ocean GCM: NEMO

Sea-ice: LIM2/3

Ice Sheets

Hazeleger et al., 2010

Sterl et al., 2011

ECMWF system

Current EC-Earth addition

Off-line in EC-Earth

modeled sea level control simulation
Modeled sea level – control simulation

Control run: 600 years,fixed preindustrial forcing

Model sea level includes:

  • Non-global steric variations (both S and T)
  • Dynamic variations

But not global mean steric changes

Area means over 3 selected areas show multidecadal variability

North Atlantic

Nordic Seas

Arctic Ocean

2099

low frequency variability
Low frequency variability
  • Decadal and longer variability relative to total variability
  • More long-term variability in the North Atlantic than in the North Pacific
  • Strong Arctic signals
low frequency variability1
Low frequency variability

All three areas included in observational study show large natural multidecadal variability

modelled historic sea level signal
Modelled “historic” sea level signal
  • Simulation 1850-now, statistical representation of historic development
  • Two ensemble members shown
  • No agreement on 1940’es warming. This indicates natural varia-bility
  • Recent years above ave-rage, must be overlain with global signal (needs further analysis)

North Atlantic

Nordic Seas

summary
Summary
  • Observations and model show that the North Atlantic and the Arctic Ocean are areas with large multidecadal variability in sea level.
  • The Norwegian/Russian sea level curve shows high values in the 1940-1950, model results indicate that it is due to natural variability.
  • The three observed sea level curves analysed here agree well in recent years and show relatively large trends after about 1990.
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