Transcript Presentation - Copernicus.org

Past and ongoing changes in the
North Sea and its interface regions
www.noc.ac.uk
John Huthnance, Ralf Weisse and NOSCCA team
NOSCCA
Temperature, salinity, stratification; circulation
Sea level, surges, waves
Carbon/pH, oxygen
SPM, morphology, Wadden Sea; ice
Summary conclusions
Part of NOSCCA Chapter 2
Ch 2 - Past and current climate change - includes
Atmosphere; North Sea; Hydrology and Vegetation
North Sea team
John Huthnance, Ralf Weisse;
Thomas Wahl, Helmuth Thomas, Julie Pietrzak, Alex Souza,
Sytze van Heteren, Natalija Schmelzer, Justus van Beusekom;
Franciscus Colijn, Ivan Haigh, Solfrid Hjøllo, Jürgen Holfort, Liz Kent,
Wilfried Kühn, Peter Loewe, Ina Lorkowski, Kjell-Arne Mork,
Johannes Pätsch, Markus Quante, Lesley Salt, John Siddorn,
Tim Smyth, Andreas Sterl, Philip Woodworth
North Sea past and ongoing - Scope
OSPAR greater North Sea to 5°W, 61°N
temperature, salinity and stratification;
currents and circulation;
mean sea level, extreme sea levels (contributions
from wind generated waves and storm surges);
CO2, pH and nutrients; oxygen;
suspended matter and turbidity;
sedimentation, morphology and coastal erosion
sea ice; Wadden Sea.
“past and ongoing”: 200 years up to the present.
Temperature trend
North Sea averaged SST annual anomalies,
1870-2013 c.f. 1971-2000 (Elizabeth Kent)
Annual and seasonal mean
North Sea heat content / 107J/m3
1950-2007 (Meyer et al. 2011)
Temperature linear trend distributions
SST trends (°C/decade) 1983-2012
from HadISST1 (Dye et al. 2013)
(L to R) 1985–2004 model near-bed
temperature, satellite SST, 2 m ERA40
air temperature (Holt et al. 2012)
Salinity
Linear trend / decade,
winter bottom salinity,
from IBTS Q1 1971-2012
(Dye et al. 2013)
Winter bottom salinity from IBTS at Viking
Bank, Dogger Bank and German Bight,
& annual mean salinity, Helgoland Roads
(Holliday et al. 2010)
Stratification
S-N section, potential temperature (°C)
near 2½°E (further E around Dogger Bank)
August 2010 (Queste et al. 2013)
Energy needed to mix water column (model,
log scale, 1 Aug. 2001; Holt & Proctor 2008)
Modelled timing of spring
stratification (Ttop – Tbottom >
0.5°C for ≥ 3 days; solid line)
and spring bloom (dashed line),
1974-2003 in 60 m water near
1.4°W 56.2°N (Sharples et al. 2006)
Currents / Circulation
Multiple forcings → various time & space scales
Measurements sparse c.f. short scales
→ trends less significant, hard to discern or diagnose causes
Reliance on models
Improvements wanted (models & observations) (√ tides, surges)
L: transport EOF1 (75.8% of variability) from
1962-2004 simulation (Emeis et al. 2014).
R: EOF1
time series
(red), NAO
index (blue;
Hurrell et al.
2013)
Mean and high sea levels
Considerable inter-annual and decadal variability in waves
(Upper inset) MSL index for Inner North
Sea (black) & non-linear SSA smoothed
(red); (lower inset) MSL index for the
Channel (black) & non-linear SSA
smoothed (red); Wahl et al. (2013);
(colour) Standard deviation from detrended annual MSL time series;
(Bottom) Cuxhaven annual mean high
water and linear trend (m), 1843-2012;
(Top) annual 99-percentile of high-tide
levels at Cuxhaven after subtracting
linear trend in annual mean; 11-year
running mean is shown (red). After von
Storch and Reichardt (1997).
carbon, oxygen
5šW 0š
a)
60šN
5šW 0š 5šE 10šE
5šE 10šE
60šN
55šN
55šN
50šN
50šN
5šW
0š
-50
5šE
10šE
0
50
DIC anomaly (2001)mmol
[
5šW 0š
60šN
55šN
50šN
-50
50šN
50šN
5šW
0š
5šE
10šE
0
50
Simulations show enhanced CO2
uptake as atmospheric pCO2
increases, acidifying the North
Sea (Lorkowski et al. 2012).
DIC anomaly (2005)mmol
[
kg-1 ]
5šW 0š 5šE 10šE
60šN
0š
55šN
-50
kg-1 ]
55šN
50šN
5šW
60šN
55šN
5šE 10šE
c)
b)
60šN
5šE
10šE
0
50
DIC anomaly (2008)mmol
[
kg-1 ]
60šN
d)
60šN
55šN
50šN
5šW
55šN
50šN
0š
2100
5šE
10šE
2200
average DIC (2001/5/8)
mmol
[
kg-1 ]
Surface DIC, August / September
2001, 2005, 2008 (Salt et al. 2013);
anomalies relative to the average
(bottom right). (Helmuth Thomas)
August 2010
bottom 3 m
oxygen
saturation (%)
& 70 %
saturation
contour
(Queste et al.
2013)
Suspended Particulate Matter
Varies with
Tides
Waves
Stratified
river flow
season
SPM monthly averages from SeaWiFs, 1998 (Pietrzak et al. 2011)
Inset pixel value colour bars (x-axis) & histograms (white, y-axis)
Coastal erosion, sedimentation, morphology
Cliff-top retreat rates at Holderness
calculated in three approximate-50year periods. Areas defended in
2005 are in grey. Retreat rates vary
within each zone. (Brown 2008)
Ice
German North Sea coast for 1897 to 2012: annual accumulated areal ice
volume V(AΣ) = ∫(fractional area × thickness)dt (days). Update from
http://www.bsh.de/de/Meeresdaten/Beobachtungen/Eis/Eiswinter2010_11.pdf
Wadden Sea
Mean autumn ammonium and nitrite: pre-industrial times, 1960-1962
(Postma 1966), 5 wettest (1986-1988, 1994, 1995) and 5 driest years (19911993, 1996, 1997) in 1986-1997, 2000-2006; western Dutch Wadden Sea (van
Beusekom & de Jonge 2002; van Beusekom et al. 2009). Latter three with
standard deviation.
Summary conclusions – no surprises!
- strong evidence of warming, especially since the 1980s,
despite temperature variability on all time-scales
- shorter-term variations in salinity > climate-related changes
- absolute mean sea level in the North Sea rose ~ 1.6 mm/year
over the past 100-120 years
- extreme levels rose primarily because mean sea level rose
- net CO2 uptake from atmosphere
- North Sea is net nitrogen sink for the Atlantic
- suspended matter and turbidity are very variable
- coastal erosion is extensive but irregular.
Thank you for your attention
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