203
European Space Agency funded OceanFlux Greenhouse
Gases project. Results from my study indicate that the variability in wind speed and, hence, the gas transfer velocity,
generally play a major role in determining the temporal variability of CO 2 uptake, while variability in monthly ΔpCO 2
plays a major role spatially, with some exception.
2.2.6 The Winter Stratification on the East
Siberian Shelf
Imke Sievers
1*
, Göran Björk
1
, Karen Assmann
1
1
Department of Marine Sciences, University of
Gothenburg, Carl Skottsbergsgata 22B, 41319 Gothenburg,
Sweden
*corresponding author: imke-s@gmx.de
Keywords: East Siberian Shelf, Mixing, 1-D modeling,
Methane transport, Sub-sea permafrost
One of the climate relevant processes in the Arctic is the
release of methane from the thawing sub-sea permafrost and
sediments in the shelf regions. The escape of methane to the
atmosphere is very much dependent on the density stratification on the shelf. The stratification is controlled by freshwater supply from rivers, exchange of water between the shelf
and the outside deep ocean, ice production, ice export and
wind forcing. The focus of this study was to make computations, using a 1D model of the development of winter stratification from wind data, air temp, river water supply and ice
export in order to quantify how far out from the coast the
shelf can be well mixed during winter and under which conditions. By answering this it also aimed to contribute to our
understanding of the methane release from shelf regions.
2.2.7 Eddy-Resolving Simulation of the Atlantic
Water Circulation in the Fram Strait
Claudia Wekerle
1*
, Qiang Wang
1
, Wilken-Jon von Appen
1
,
Sergey Danilov
1
, Vibe Schourup-Kristensen
1
, Thomas Jung
1
1
Alfred Wegener Institute, Helmholtz Centre for Polar
and Marine Research, Bremerhaven, Germany
*invited speaker, corresponding author: claudia.wekerle@
awi.de
Keywords: Ocean modeling, Unstructured meshes, Fram
Strait, Arctic Ocean
The Fram Strait is the deepest and widest gateway that
connects the Arctic Ocean with the Nordic Seas and thereby
the Atlantic Ocean, thus being the major place for heat and
water mass exchange. The two main currents responsible for
the exchange are the West Spitsbergen Current (WSC) on the
eastern side of Fram Strait transporting warm and salty
Atlantic Water (AW) northward, and the East Greenland
Current on the western side carrying cold and fresh Polar
Water southward. Eddy driven recirculation of AW in the
Fram Strait modifies the amount of heat that reaches the
Arctic Ocean, but is difficult to constrain in ocean models
due to very small Rossby radius there. Here we explore the
effect of resolved eddies on the AW circulation in a locally
eddy-resolving simulation of the global Finite-Element-Sea
ice-Ocean-Model (FESOM). An eddy-permitting simulation
serves as a control run. Our results suggest that resolving
local eddy dynamics is critical to realistically simulate ocean
dynamics in the Fram Strait. Strong eddy activity simulated
by the eddy-resolving model, with peak in winter and lower
values in summer, is comparable in magnitude and seasonal
cycle to observations from a long-term mooring array,
whereas the eddy-permitting simulation underestimates the
observed magnitude. Furthermore, a strong cold bias in the
central Fram Strait present in the eddy-permitting simulation
is reduced due to resolved eddy dynamics, and AW transport
into the Arctic Ocean is increased with possible implications
for the Arctic Ocean heat budget. Given the good agreement
between the eddy-resolving model and measurements, it can
help filling gaps that point-wise observations inevitably
leave. For example, the path of the WSC offshore branch,
measured in the winter months by the mooring array, is
shown to continue cyclonically around the Molloy Deep in
the model, representing the major AW recirculation branch
in this season.
2.3 Abstracts of Poster Presentations
2.3.1 Wind Forcing of the Arctic and North
Atlantic Freshwater System
Tamas Kovacs
1*
, Rüdiger Gerdes
1,2
1
Alfred-Wegener-Institut, Helmholtz-Zentrum für Polarund Meeresforschung, Am Handelshafen 12, 27570
Bremerhaven, Germany
2
Jacobs University Bremen gGmbH, Bremen, Germany
*corresponding author: tamas.kovacs@awi.de
Keywords: Arctic Ocean, Modeling, Freshwater,
Atmospheric forcing
Oceanic processes in the Arctic and in the North Atlantic
that play a key role in the global ocean circulation are often
sensitive to density stratification of water, which is greatly
shaped by salinity, or in another measure, by freshwater content. The freshwater budgets of these oceans are connected
by currents that convey large volumes of water of different
characteristics between one another. However, these budgets
show spatial and temporal variations, and the fluxes between
them cannot be considered constant either. The freshwater
system of the Arctic linked to the North Atlantic is dynamic
with changes and anomalies on different time scales, and the
changes of this joint system seem to be in correlation with
the evolution of atmospheric forcing patterns. Previous studies suggest the importance of wind stress forcing over key
regions such as the Beaufort Sea or the Greenland Sea in
influencing the distribution of freshwater. In this study we
examine the sensitivity of freshwater distribution and fluxes
Appendices
European Space Agency funded OceanFlux Greenhouse
Gases project. Results from my study indicate that the variability in wind speed and, hence, the gas transfer velocity,
generally play a major role in determining the temporal variability of CO 2 uptake, while variability in monthly ΔpCO 2
plays a major role spatially, with some exception.
2.2.6 The Winter Stratification on the East
Siberian Shelf
Imke Sievers
1*
, Göran Björk
1
, Karen Assmann
1
1
Department of Marine Sciences, University of
Gothenburg, Carl Skottsbergsgata 22B, 41319 Gothenburg,
Sweden
*corresponding author: imke-s@gmx.de
Keywords: East Siberian Shelf, Mixing, 1-D modeling,
Methane transport, Sub-sea permafrost
One of the climate relevant processes in the Arctic is the
release of methane from the thawing sub-sea permafrost and
sediments in the shelf regions. The escape of methane to the
atmosphere is very much dependent on the density stratification on the shelf. The stratification is controlled by freshwater supply from rivers, exchange of water between the shelf
and the outside deep ocean, ice production, ice export and
wind forcing. The focus of this study was to make computations, using a 1D model of the development of winter stratification from wind data, air temp, river water supply and ice
export in order to quantify how far out from the coast the
shelf can be well mixed during winter and under which conditions. By answering this it also aimed to contribute to our
understanding of the methane release from shelf regions.
2.2.7 Eddy-Resolving Simulation of the Atlantic
Water Circulation in the Fram Strait
Claudia Wekerle
1*
, Qiang Wang
1
, Wilken-Jon von Appen
1
,
Sergey Danilov
1
, Vibe Schourup-Kristensen
1
, Thomas Jung
1
1
Alfred Wegener Institute, Helmholtz Centre for Polar
and Marine Research, Bremerhaven, Germany
*invited speaker, corresponding author: claudia.wekerle@
awi.de
Keywords: Ocean modeling, Unstructured meshes, Fram
Strait, Arctic Ocean
The Fram Strait is the deepest and widest gateway that
connects the Arctic Ocean with the Nordic Seas and thereby
the Atlantic Ocean, thus being the major place for heat and
water mass exchange. The two main currents responsible for
the exchange are the West Spitsbergen Current (WSC) on the
eastern side of Fram Strait transporting warm and salty
Atlantic Water (AW) northward, and the East Greenland
Current on the western side carrying cold and fresh Polar
Water southward. Eddy driven recirculation of AW in the
Fram Strait modifies the amount of heat that reaches the
Arctic Ocean, but is difficult to constrain in ocean models
due to very small Rossby radius there. Here we explore the
effect of resolved eddies on the AW circulation in a locally
eddy-resolving simulation of the global Finite-Element-Sea
ice-Ocean-Model (FESOM). An eddy-permitting simulation
serves as a control run. Our results suggest that resolving
local eddy dynamics is critical to realistically simulate ocean
dynamics in the Fram Strait. Strong eddy activity simulated
by the eddy-resolving model, with peak in winter and lower
values in summer, is comparable in magnitude and seasonal
cycle to observations from a long-term mooring array,
whereas the eddy-permitting simulation underestimates the
observed magnitude. Furthermore, a strong cold bias in the
central Fram Strait present in the eddy-permitting simulation
is reduced due to resolved eddy dynamics, and AW transport
into the Arctic Ocean is increased with possible implications
for the Arctic Ocean heat budget. Given the good agreement
between the eddy-resolving model and measurements, it can
help filling gaps that point-wise observations inevitably
leave. For example, the path of the WSC offshore branch,
measured in the winter months by the mooring array, is
shown to continue cyclonically around the Molloy Deep in
the model, representing the major AW recirculation branch
in this season.
2.3 Abstracts of Poster Presentations
2.3.1 Wind Forcing of the Arctic and North
Atlantic Freshwater System
Tamas Kovacs
1*
, Rüdiger Gerdes
1,2
1
Alfred-Wegener-Institut, Helmholtz-Zentrum für Polarund Meeresforschung, Am Handelshafen 12, 27570
Bremerhaven, Germany
2
Jacobs University Bremen gGmbH, Bremen, Germany
*corresponding author: tamas.kovacs@awi.de
Keywords: Arctic Ocean, Modeling, Freshwater,
Atmospheric forcing
Oceanic processes in the Arctic and in the North Atlantic
that play a key role in the global ocean circulation are often
sensitive to density stratification of water, which is greatly
shaped by salinity, or in another measure, by freshwater content. The freshwater budgets of these oceans are connected
by currents that convey large volumes of water of different
characteristics between one another. However, these budgets
show spatial and temporal variations, and the fluxes between
them cannot be considered constant either. The freshwater
system of the Arctic linked to the North Atlantic is dynamic
with changes and anomalies on different time scales, and the
changes of this joint system seem to be in correlation with
the evolution of atmospheric forcing patterns. Previous studies suggest the importance of wind stress forcing over key
regions such as the Beaufort Sea or the Greenland Sea in
influencing the distribution of freshwater. In this study we
examine the sensitivity of freshwater distribution and fluxes
Appendices