Seasonal and interannual variability in hydrography and currents along the Nansen Legacy transect across the Barents Sea
Permanent lenke
https://hdl.handle.net/10037/34073Dato
2023-12-20Type
Master thesisMastergradsoppgave
Forfatter
Sortland, Julie Marie SeimeSammendrag
The Barents Sea is an Arctic shelf sea that is an important site forwater mass formation
and transformation. It is characterized by interactions between Atlanticand
Arctic-originWaters, and by strong seasonality in terms of alternating atmospheric
and sea-ice conditions throughout the year. How these aspects impact
the seasonal evolution of the water column properties is yet to be fully understood.
In this study, we investigate the hydrographic conditions along the
Nansen Legacy (NL) main transect across the Barents Sea and towards the
adjacent Nansen Basin in the Arctic Ocean in the period between 2018 and
2022. In particular, we describe the dominant water masses and currents along
the transect and investigate the seasonal and interannual variations in water
mass characteristics, distribution, and circulation. The dataset includes CTD,
S-ADCP, and L-ADCP profiles collected through the NL project. Ancillary data
includes atmospheric reanalysis and remotely sensed sea ice data, used to assess
how atmospheric and sea ice forcing alters the water column throughout
the study period.
Our analysis shows that the NL transects can be divided into three domains
reflecting differences in water masses, seasonal evolution, heat- and freshwater
content, and flow regimes. In the Nansen Basin and at the Svalbard Continental
shelf (81-82◦ N), the circulation is shaped by the water that is advected in
with the AtlanticWater Boundary Current (AWBC) at intermediate depths. The
seasonal variations of the AWBC further control the seasonal variations in hydrographic
properties in the area, for example in the form of elevated oceanic
temperatures during autumn/ early winter. In general, the water column structure
in the region follows the typical layering with Polar Water (PW) and/or
warm Polar Water (wPW) on top followed by Atlantic Water (AW), modified
Atlantic Water (mAW), and Eurasian Basin Deep water (EBDW).
The Northern Barents Sea (77-81◦ N) is mainly dominated by PW in the upper
water column and wPW at lower depths. The water is overall cold and fresh,
characteristic of an Arctic domain. The hydrographic properties in the upper
water column are shaped by the presence of sea ice cover, which often is extensive
during winter and spring in this area. We find that the sea ice cover
controls the heat and freshwater content, the stratification, and shape the water masses in the area.
South of the Polar Front (<76.8◦ N), warm Atlantic-origin waters dominate
the area. On a yearly cycle, the water column progresses from a three-layer,
relatively stratified column with wPW, AW, and mAW during summer, to a
homogeneous water column consisting of cooled mAW during winter. Here,
the water column properties appear to be controlled by local processes, rather
than advective ones.
Forlag
UiT Norges arktiske universitetUiT The Arctic University of Norway
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