1. What does the ‘Gulf Stream’ have to do with sea level?

2. Sea level projections for Norway to 2100
Regional
steric/dynamic
contribution:
Large
Most uncertain
Decadal variability
RCP8.5
m/100 yr
∆RSL
Stavanger
meter
Contributions RCP4.5
The projected time series (RCP2.6 green; RCP4.5 blue; RCP8.5 red).
Only small differences between the RCPs before 2050.
Uncertainties best represented by observed (yellow) natural variability the next few decades.
In the latter half of the century the separate projections from RCPs diverge but still large overlaps between the likely ranges (shaded areas, and bars for 2081–2100 means).
Figure 5.2 Contributions to projected relative sea level change for RCP4.5 over the period 1986–2005 to 2081–2100 for the six key locations (a) Oslo (b) Stavanger (c) Bergen (d) Heimsjø (e) Tromsø and (f) Honningsvåg. The ensemble mean and -spread (5 to 95%) are shown by the circles and vertical bars, respectively. --
The Norwegian Environment Agency
The Norwegian Mapping Authority
Norwegian Meteorological Institute
Norwegian Water Resources and Energy Directorate
University of Oslo
Norwegian Directorate for Civil Protection
Simpson et al (2015)

3. Consequence of mean sea level rise50
100
150
200
250
300
-50
-100
350
TV2
Higher levels
More frequent flooding
By 2100:
Today:
20 yrs, Jan Lillebø/BT 2005
Weather effects
1 yrs
200 yrs
20 yrs
1000 yrs
200 yrs
Hva skjer med stormfloer?
Vi kjenner frekvens og høyde på stormflohendelser i dag.
Vi har ikke grunnlag for å forvente endring i stormaktiviteten.
Observasjoner viser hvor mye og hvor ofte været gir høyere havnivåer.
For eksempel Bryggen i Bergen … <forklaring/animasjon> … Her opplever man stormfloer som går over kaikanten. Sist i 2007, hvor vi hadde det som kalles en 20-års stormflo.
Når havet stiger, løftes alle nivåene, noe som gjør at svakere, mer frekvente stormflonivåer også medfører oversvømmelser.
I Bergen kan oversvømmelse bli en årlig foreteelse før midten av århundret. Utslippsendringer kan bare forsinke dette med et tiår eller to. (20 års; )
HOVEDPOENG: Høyere nivåer + oftere oversvømmelser.
Innledng til neste: Hvor fort hyppigheten endrer seg avhenger både av havnivåstigning OG hvor langt det er mellom stormflonivåene. …
1990: 1000 års; års
Tides
50 cm sea level rise
LAND MAP ZERO
Frequency
kartverket.no/sehavniva

4. Contributions to coastal sea level variability and change
Vertical land motion
Static atmospheric pressure
Thermal expansion
Haline contraction …

5. An ‘early’ study Relative sea level (RSL): Tide-gauges
Richter et al. (2012)
Relative sea level (RSL):
Tide-gauges
Vertical land movement:
Combined GPS, leveling, and tide gauge recordings
Atmospheric variability:
NCEP-NCAR sea level pressure
Changing hydrography:
Permanent CTD stations
Tide gauges (monthly)
Peltier’s model is global, so small scale anomalies in Earth’s structure are not properly modeled. Therefore, we use the data set provided by Vestøl. At TG positions.
The pressure fluctuations are defined as the deviations from the mean over the period 1960–2010. (In general, a 1 mbar increase in surface pressure produces a 1 cm depression). Monthly.
IMR, twice a month in general

6. The reconstruction - Richter et al. (2012) Example: Bergen
Figure 4. Contributions from land uplift, IBE, and thermosteric and halosteric heights to RSL variability in Bergen. For better visualization, the monthly time series have been low pass filtered by applying a 1 year running mean.
To the bottom.

7. Observations and reconstruction
Richter et al. (2012)
Good agreement between reconstruction and observation
Residuals show positive trend (1.5 mm/yr);
Bergen

8. There are more contributions
Melting of land based ice and hydrology
Nodal cycle
Shelf mass loading
Large scale steric variability
Wind
Currents

9. The nodal cycle
The tide on the Earth is driven by six different forcing components with periods varying from 1/2 day to 20,940 years
The nodal cycle has 18.6 year period
Moon’s orbital plane precesses in a retrograde sense (draconian month is shorter than sidereal month).

10. The effect of thermal expansion (and haline contraction)
The water is expanding, but still the same ‘amount’ of water at each location.
NorESM :
Fremtid, for modellene kan separere effektene, det er ikke mulig i obs.
Og for å peke litt til fremskrivninene.
Mengde = Masse, antall molekyler.
Richter et al (2013)

11. … and shelf mass loading
Expansion at depth pushes water onto shallower regions
This is mass redistribution, not to be confused with local thermal expansion!
Steric expansion and mass loading together results in a more evenly distributed rise.
Change in mass of water
NorESM :
Expansion deeper than
700 m
Dypere enn 700 m
A “hybrid”: Steric change -> mass redistribution
Richter et al (2013)

12. Norwegian Budget Where do the steric signals come from?
Frederikse et al (2016)
Correlation
North Sea SL
and steric SL
Where do the steric signals come from?
And how do they get onto the shelf?
Figure 2. (top) Measured relative sea level, together with the contributing processes, (middle) the sum of the contributing processes, and (bottom) the residual RSL. The shaded areas denote one standard error (sum of contributors) and the spread between the different tide gauge stations (measured RSL). (left column) North Sea station and (right) Norway stations. All time series have been low-pass filtered with a 25 month running mean.
local wind and pressure removed.
Figure 1. (a) Location of the tide gauges for each region, Ocean Weather Station Mike (OWSM), and bathymetry.
(b) Correlation between TG sea level in the North Sea after removing all mass contributors and steric height computed
at each grid point from the surface to the seafloor or 1000 m, depending on which is reached first. (c) Correlation
between TG sea level in the North Sea and sea level observed by satellite altimetry between 1993 and The grey
line depicts the 1000 m isobath. All time series have been detrended and low-pass filtered using a 25 month running
mean, and all mass contributors have been removed before computing the correlation.

13. On-shelf variability is coherent
EOF1 of monthly altimetry on shelf
51%
Chafik et al. (2017)

14. Wind forcing of on-shelf sea level variability
Figure 13. Composite difference of sea level from altimetry (m, shading), MSLP (hPa, contours)
and 10-m winds (arrows) based on (a) the on-shelf and (b) the TG PC1s. The sea level, MSLP
and winds have deseasoned and detrended before the composite analysis, which is based on the
difference between anomalously high (>0.75 std) and low (<-0.75 std) periods in the PC1s. The black
contour denotes the zero MSLP anomaly, while the blue/red contours denote negative/positive MSLP
anomaly with a spacing of 2 hPa. (c) Schematic diagram including the main dynamical processes
involved on monthly timescales. This case reflects southerly along-shelf/shore winds that through
Ekman transports increase the coastal sea level. The non-significant regions below the 95% confidence level are indicated by gray crosses calculated using a two-sided t test.
Chafik et al. (2017)

15. Sea level and slope currents
Composite sections: high vs. low on-shelf sea level
High
Low
Chafik et al. (2017), Raj et al. (in prep.)

16. Strong relation with the slope current
Slope current at Svinøy section regressed on sea level
Figure 2: Strong relation with the Slope Current. Slope Current speeds regressed onto sea-surface heights (m) from satellite altimetry (AVISO) during the 1995–2015 period (see Chafik et al., 2015). The Slope Current speeds are based on current-meter data located at the shelf slope in the core of the flow at Svinøy (Courtesy of K.-A. Orvik; see Orvik et al., 2001). The sea-surface height gradient observed along the shelf slope is an indication of wind-induced Ekman transport that decreases the sea-level in the interior while piling up water on the shelves.
Chafik et al. (2015); Orvik et al. (2001)

17. Correlation with the slope current
On-shelf mode & slope current
Tide gauge in Trondheim & slope current
See also Richter et al. (2012b)

18. Takk for meg!

19. References
Chafik, L., J. Nilsson, Ø. Skagseth, and P. Lundberg (2015), On the flow of Atlantic water and temperature anomalies in the Nordic Seas toward the Arctic Ocean, J. Geophys. Res. Oceans, 120, doi: /2015JC Chafik, L., J.E.Ø. Nilsen, S. Dangendorf (2017). Impact of North Atlantic teleconnection patterns on Northern European sea level. J. Mar. Sci. Eng., 5, 43, doi: /jmse Frederikse, T., R. Riva, M. Kleinherenbrink, Y. Wada, M. van den Broeke, and B. Marzeion (2016), Closing the sea level budget on a regional scale: Trends and variability on the Northwestern European continental shelf, Geophys. Res. Lett.,43, doi: /2016GL Orvik, K. A., Ø. Skagseth, and M. Mork (2001), Atlantic inflow to the Nordic Seas: Current structure and volume fluxes from moored current meters, VM-ADCP and SeaSoar-CTD observations, 1995–1999, Deep Sea Res., Part I, 48(4), 937–957. Richter, K., J.E.Ø. Nilsen, H. Drange (2012). Contributions to sea level variability along the Norwegian coast for J. Geophys. Res., 117, C05038, doi: /2009JC Richter, K., O. H. Segtnan, and T. Furevik (2012b). Variability of the Atlantic inflow to the Nordic Seas and its causes inferred from observations of sea surface height, J. Geophys. Res., 117, C04004, doi: /2011JC Richter, K., R. E. M. Riva, H. Drange (2013). Impact of self attraction and loading effects induced by shelf mass loading on projected regional sea level rise. Geophys. Res. Lett., 40 (1–5), doi: /grl Simpson, M.J.R., J.E.Ø. Nilsen, O.R. Ravndal, K. Breili, H. Sande, H.P. Kierulf, H. Steffen, E. Jansen, M. Carson and O. Vestøl (2015). Sea Level Change for Norway: Past and Present Observations and Projections to Norwegian Centre for Climate Services report 1/2015, ISSN , Oslo, Norway. 155 pp. doi: /RG