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Arctic Gateway Transport and Sensitivity in the ANHA NEMO Configuration
http://ns.umich.edu/Releases/2011/Apr11/Arctic14.jpg
Paul G. Myers, Xianmin Hu, Laura Castro de la Guardia, Nathan Grivault, Juliana Marson, Clark Pennelly, Natasha Ridenour, Laura Gillard, Department of Earth and Atmospheric SciencesUniversity of Alberta
Outline
• ANHA NEMO Configuration
• Freshwater Processes
• Sensitivity
• Forcing
• ERA-Interim, COREv2/NCEP, JRA55-do, DFS5.2, CGRF
• Resolution
• ½ degree, ¼ degree, 1/12 degree
• Tides
• Runoff
• Summary
ANHA: Arctic NorthernHemisphere Atlantic
NO temperature & salinity restoring
Model: [ocean] NEMO 3.4[sea ice] LIM2
Period: 2002-2016
Initialization: GLORYS2v3
3D Ocean fields: T, S, Velocity
SSH and sea ice
Atmosphericforcing: CGRF
Hourly @ 33km resolutionWinds, Temperature, HumidityPrecipitation, Radiation (SW & LW)
Runoff: monthly interannual Dai and Trenberth’s runoffJ. Bamber’s Greenland melt (2012)
OBC: GLORYS2v3Ocean velocity, temperature and salinity
Bathymetry: ETOPO1 + Smith and Sandwelll
CGRF: Canadian Meteorological Centre’s (CMC) global deterministic prediction system (GDPS) reforecasts ETOPO1: NOAA Global data set ERA: Global atmospheric reanalysis GLORYS: GLobal Ocean ReanalYses & Simulations
1/12o1/4o
Resolution: 1/4o & 1/12o
CAA: ~ 10 km& ~ 4 kmLab. Sea: ~ 15 km& ~ 5 km
Mesh: 544 x 800 & 1632 x 2400
50 levels
1/12o
Pacific Water Pathway in the Arctic Ocean
Revealed by Online Passive Tracer in NEMO
Simulations: by Xianmin Hu and Paul G. Myers
1. Passive Tracer introduced at Bering Strait
in ¼ and 1/12 degree NEMO Simulations
2. Pacific Water pathways match the contours
of freshwater content
3. Beaufort Gyre freshwater budget shows key role of
surface processes, as well as lateral exchange4. Eddies play a key role in
balancing budget at 1/12 degree
7North South
Dep
th
TW
Heat Transport along Topography: Disko Bay Section
Gillard et al., [email protected]
On shelf
Off shelf
INTERANNUAL
JI retreat
NASPG warming ??
8
On shelf
Off shelf
Moving Average
Transient
𝒖 = 𝒖 + 𝒖′Heat Flux Through Disko Trough
On shelf
Off shelf
𝒖 = 𝒖 + 𝒖′
Moving AverageTransient
Heat Flux Through Helheim Trough
Gillard et al., prep. [email protected]
Sensitivity ExperimentsExamine five different Atmospheric Forcing datasets
Name L.S. Spatial Resolution
Temporal Resolution Simulation length
Notes
CORE2& NCEP
130 km 6-hourDaily LW/SWMonthly Precip/snow
CORE2: 2002-2009NCEP: 2010-2016
Reanalysis
CGRF 33 km HourlySnow derived from T/precip
2002-2016 Reforecast
ERA-Interim
45 km 3-hourDaily LW/SW/precip
2002-2016 Reanalysis
DFS 5.2 45 km 3-hourDaily LW/SW/precip/snow
2002-2016 Built from ERA-Interim
JRA55-DO
31 km 3-hourly fieldsDaily runoff (not used)
2002-2016 Reanalysis
December 20, 2003:Total precipitationAverage wind speed
Flux Comparison Over Labrador Sea
Heat Loss 2004-2016
Buoyancy Loss 2004-2016
Barrow Strait
• Observations
• DFS5.2
• ERA
• COREv2/NCEP
• JRA-55
• CGRF
mean Corr to
obs.
RMS to
obs.
DFS5.2 0.96 0.36 0.57
ERA 0.93 0.43 0.54
COREv2 1.19 0.50 0.73
JRA-55 0.96 0.48 0.55
CGRF 0.63 0.43 0.41
mean Corr to
obs.
RMS to
obs.
DFS5.2 27.6 0.39 21.2
ERA 26.8 0.47 20.8
COREv2 34.2 0.50 19.5
JRA-55 27.4 0.50 20.4
CGRF 18.1 0.48 23.1
Obs: 0.5 Sv
Obs: 32 mSv
• Petersen et
al. (2012)
Barrow Strait Notes
• All Forcing products over-estimate the volume transport
• Most forcing products under-estimate the freshwater transport
• And freshwater transport linked to volume transport
• So forcing products with better freshwater transport just because volume transport to large
• Other work (Grivault et al. 2018) suggest winter and too mobile sea ice drives too large transport
• Little impact of resolution (1/2 to 1/12 degree)
• No clear impacts from tidal forcing or different runoff (very preliminary)
Impact of sea-ice motion on
transport through the Canadian
Arctic Archipelago
Grivault et al. (JGR, under review)
Grivault et al., 2018, JGR
Nares Strait
• Observations
• DFS5.2
• ERA
• COREv2/NCEP
• JRA-55
• CGRF
• Muenchow
(2016)
Obs: -1.0 Sv
Obs: -40 mSv
mean Corr to
obs.
RMS to
obs.
DFS5.2 -0.80 0.46/0.65 0.27/0.20
ERA -0.87 0.50/0.66 0.24/0.18
COREv2 -0.95 0.35/0.68 0.45/0.29
JRA-55 -1.10 0.48/0.67 0.32/0.28
CGRF -0.78 0.52/0.72 0.19/0.27
mean Corr to
obs.
RMS to
obs.
DFS5.2 -22.9 0.15/0.52 19.1/31.0
ERA -25.0 0.18/0.52 17.2/29.6
COREv2 -27.4 0.01/0.54 19.8/26.3
JRA-55 -31.5 0.18/0.57 13.6/22.9
CGRF -22.5 0.25/0.61 16.1/33.5
Nares Strait• Observations
• ½ degree
• ¼ degree
• 1/12 degree
Nares Strait Notes
• Volume transports around observational
• Generally represent transport in both periods, with better correlations in second
• Freshwater transports around observational in first period, but significantly lower in second
• Even if variability better captured in second period
• Freshwater transports tightly coupled to volume
• ½ degree resolution fails to represent transport
• No clear impacts from tidal forcing or different runoff (very preliminary)
Davis Strait
• Observations
• DFS5.2
• ERA
• COREv2/NCEP
• JRA-55
• CGRF
• Curry et al.
(2014)
mean Corr to
obs.
RMS to
obs.
DFS5.2 -1.91 0.51 0.65
ERA -1.94 0.56 0.62
COREv2 -2.36 0.50 1.00
JRA-55 -2.20 0.57 0.76
CGRF -1.50 0.66 0.64
Obs: -1.6 Sv
Obs: -94 mSv
mean Corr to
obs.
RMS to
obs.
DFS5.2 -54.8 0.16 48.1
ERA -55.5 0.23 48.1
COREv2 -67.7 0.20 42.1
JRA-55 -63.0 0.23 41.7
CGRF -43.2 0.31 61.0
Davis Strait Notes
• Volume transports generally have too much net southward transport
• Closest to observations, with highest correlations for variability, the highest resolution (spatial and temporal) product
• Significant underestimation of net southward freshwater flux
• Strong link between net volume and net freshwater
• Given Davis Strait has multiple water masses, will have to break analysis down per water mass to better understand what is happening
• Little impact of resolution (1/2 to 1/12 degree)
• No clear impacts from tidal forcing or different runoff (very preliminary)
EGC (southward flow)78.5N – Obs. Array
• Observations
• DFS5.2
• ERA
• COREv2/NCEP
• JRA-55
• CGRF
• de Steur et
al. (2014)
Obs: -7.9 Sv
mean Corr to
obs.
RMS to
obs.
DFS5.2 -6.5 0.30 3.1
ERA -6.8 0.38 2.8
COREv2 -8.6 0.35 4.1
JRA-55 -7.2 0.37 3.0
CGRF -7.3 0.35 3.0
de Steur et al. (2018):
September 2003 to August
2015: 70 ± 24.7 mSv
EGC• Observations
• ½ degree
• ¼ degree
• 1/12 degree
EGC Notes
• Volume transports generally have too little southward transport (Except CORE/NCEP)
• Significant overrestimation of net southward freshwater flux
• Strong link between net volume and net freshwater
• Given Fram Strait has multiple water masses, will have to break analysis down per water mass to better understand what is happening
• ½ degree resolution unable to represent transports
• Little impact of higher resolution (1/4 to 1/12 degree)
• No clear impacts from tidal forcing or different runoff (very preliminary)
Fram Strait
• Observations
• DFS5.2
• ERA
• COREv2/NCEP
• JRA-55
• CGRF
Mean –
vol - Sv
Mean –
fw - mSv
DFS5.2 -2.5 -70.4
ERA -2.5 -71.5
COREv2 -2.3 -66.3
JRA-55 -2.1 -60.8
CGRF -2.8 -79.2
Bering Strait Opening
• Observations
• DFS5.2
• ERA
• COREv2/NCEP
• JRA-55
• CGRF
Mean –
vol – Sv
Mean –
fw - mSv
DFS5.2 2.9 -83.9
ERA 3.0 -85.4
COREv2 3.2 -92.6
JRA-55 2.8 -81.9
CGRF 2.8 -80.6
Summary
• Pacific Water pathways match the contours of freshwater content
• Freshwater from icebergs more likely to reach the interior of the Labrador Sea
• Role of mean and transient components of the flow play different roles for driving heat into Greenland troughs on different coasts
• No clear view of which atmospheric reanalysis produces Gateway fluxes closer to observations
Future Projects
BaySys – Hudson Bay Freshwater Dynamics and Climate Change
Quantifying Canada’s Ocean Carbon Sink
• Seeking Postdoc (2019-2020)
Ridenour et al., 2019• How relevant are processes
represented in high to very high
resolution ocean models
• Seeking Postdoc (2019-2022)
