Predicting the consequences of nutrient reduction on the eutrophication status of the north sea
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Predicting the consequences of nutrient reduction on the eutrophication status of the north sea

Predicting the consequences of nutrient reduction on the eutrophication status of the North Sea

D. K. Mills, H. J. Lenhart, J.G. Baretta-Bekker, S. M. van Leeuwen, J. van der Molen, M. Blaas, W. Kühn, F.J. Los, G. Lacroix, A. Ménesguen, R. Neves, R. Proctor, P. Ruardij, J. W. Baretta, M. D. Skogen, M.T. Villars and S. L. Wakelin

Cefas, POL (UK);RWS, Deltares, NIOZ (NL), MUMM (BE), IFREMER (FR), IFM (DE), IMR (NO), IST (PT)


Ospar regional convention

OSPAR – Regional Convention

Conventionfor the protection of the marine environment of the North-East Atlantic

Strategy:to make every effort to combat eutrophication in the maritime area, in order to achieve, by the year 2010, a healthy marine environment where eutrophication does not occur.

PARCOM Recommendation 88/2:where eutrophication diagnosed then a reduction (of the order of 50%) in inputs of phosphorus and nitrogen.

OSPAR definition of eutrophication:“the enrichmentof water by nutrients, especially nitrogen and/or phosphorus, causing an accelerated growthof algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of water concerned”


Intersessional correspondance group on eutrophication modelling icg emo

Intersessional Correspondance Group on Eutrophication Modelling (ICG-EMO)

an assessment in 2006 of the expected eutrophication status of the OSPAR maritime area following the implementation of agreed measures

OSPAR ICG-EMO Planning Group:

D. Mills (Chair), J. van der Molen, S. van Leeuwen (UK, Cefas,)

H. Barretta-Bekker (NL, RWS), H. Lenhart (DE,IfM)

OSPAR class. according to Common Procedure

23 participants, 10 institutes, 7 nationalities, 8 models

1st Workshop in Hamburg (IfM, September 2005)

2nd Workshop in Lowestoft (Cefas, September 2007)

3rd Workshop, September 2009 (MUMM, Belgium)

Problem Area

Potential Problem Area


Icg emo use common forcing

N: NORWECOM

UK Cefas:

GETM-BFM

PT: MOHID

NL: Delft3D

B: MIRO

FR: ECO-MARS

DE: ECOHAM

ICG-EMO: use common forcing

  • Provided by ICG-EMO

  • boundary conditions

  • riverine loads

  • atmospheric deposition fields

  • meteorological forcing

  • spin up procedure

  • calibration and validation data

UK POL: POLCOMS-ERSEM


Icg emo use common forcing1

ICG-EMO: use common forcing

  • Provided by ICG-EMO

  • boundary conditions (POL)

  • riverine loads

  • atmospheric deposition fields

  • meteorological forcing

  • spin up procedure

  • calibration and validation data

1985

2002

ammonium

Different load reductions for TOxN (NO2+NO3), NH4 and PO4

Different load reductions for each country


Nutrient reduction scenarios

Nutrient reduction scenarios


Icg emo procedure

ICG-EMO: procedure

  • Provided by ICG-EMO

  • boundary conditions (POL)

  • riverine loads

  • atmospheric deposition fields

  • meteorological forcing

  • spin up procedure

  • calibration and validation data

ECMWF operational reanalysis

≥ 3 years

NSP 1989 and ‘monitoring’ data for 2002

Standard year 2002

  • reference run

  • 50% reduction with respect to 1985

  • 70% reduction with respect to 1985

Comparable results due to

common forcing and procedure


Predicting the consequences of nutrient reduction on the eutrophication status of the north sea

50% red.-standard

standard

Winter DIN results

NL

DE

BE

UK Cefas


Ospar target areas

OSPAR target areas

10 target areas for model intercomparison

Water body definitions:

Catchment, hydrography & salinity

O = offshore (>34.5 salinity)

C=coastal (30-34.5 salinity)

e.g. NLO2 is the Netherlands Offshore target area 2.

UK-C1

NL-O2


Predicting the consequences of nutrient reduction on the eutrophication status of the north sea

UK-C1 results

Parameter response to 50% reduction

Parameter response to 70% reduction

Annual O2 mini- mum at bottom

Mean winter DIP at surface

Mean winter DIN at surface

Mean summer Chl at surface


Assessment of eutrophication

mean

Chla

max

Chla

min O2

DIN

DIP

N/P

0%

50%

threshold

70%

Assessment of eutrophication

Cefas GETM-BFM results for UK-C1


Assessment of eutrophication1

mean

Chla

max

Chla

min O2

DIN

DIP

N/P

+

0

threshold

Assessment of eutrophication

Cefas GETM-BFM results for UK-C1


Predicting the consequences of nutrient reduction on the eutrophication status of the north sea

NL-O2 results

Model results presented in OSPAR

Comprehensive Procedure reporting format


Results

Largest reductions in nutrients parameters are seen in the coastal water target areas.

A strong, almost linear response in winter DIN concentrations to the reduced loads (less in DIP).

Winter DIP concentrations do not respond as strongly to the load reductions as DIN with a decrease of up to 30% with 70% reduction in UK coastal waters but results are typically < 30% for all other areas and scenarios.

The range of responses in mean summer chlorophyll concentration is 4% - 25% with similar minimum decreases in coastal and offshore waters but the maximum decreases in coastal waters are nearly double those achieved in offshore areas for both scenarios.

Minimum dissolved oxygen concentration increased by a maximum of 12% for 70% reduction in coastal waters. Offshore and coastal waters gave similar results for both scenarios.

Results

In general all models exhibit the following characteristics:


Conclusions

Comparability of models improved through common boundary conditions, calibration and validation data

Models can support (in part) formal assessments of eutrophication

Setting wider context to assessment outcome

Determine robustness of eutrophication indicators

Improve interpretation of indicator values e.g. min O2 conc

Help set background levels i.e. pristine values of indicator

Insight into future eutrophication status for some target areas

Only quantitative method for evaluating mitigation measures i.e. nutrient reduction

Trends more reliable that than absolute values

Conclusions

See ‘www.cefas.co.uk/eutmod’ for full report on workshop


Forward look

Forward look

2nd ICG-EMO workshop report on www.cefas.co.uk/eutmod/

Revised 2nd workshop report submitted (including French and Belgium target areas) as stand-alone document

3rd workshop to be held in Belgium (MUMM), September 2009

Focus on calculating transboundary nutrient transport

Approach

  • budgets across transects

  • tagged nutrients – trace to source


Predicting the consequences of nutrient reduction on the eutrophication status of the north sea

Thank you for your attention!

Thanks to the OSPAR ICG-EMO workshop participants

2nd row: A. Weiss (OSPAR), R. Proctor (UK), B. Brinkman (NL), M. Villars (NL), W. Kühn (DE), G. Lacroix (B), J. Baretta (NL), M. Blaas (NL), T. Prins (NL), M. Sourisseau (F), P. Ruardij (NL), J. van der Molen (UK)

1st row: M. Skogen (NO), L. Fernand (UK), H. Los (NL), S. M. van Leeuwen (UK), H. Lenhart (DE), H. Baretta-Bekker D.Mills (UK), S. Wakelin (UK), B. Bernardes (PT), A. Ménesguen (F), R. Neves (PT)


Nl o2 results

NL-O2 results

Parameter response to 50% reduction

Parameter response to 70% reduction

Mean winter DIN at surface

Mean winter DIP at surface

Mean summer Chl at surface

Annual O2 mini- mum at bottom


Uk c1 results

UK-C1 results

Model results presented in OSPAR

Comprehensive Procedure reporting format


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