1: Arctic Fjords Flashcards
The fjords circulation is dependent on
- Wind forcing - Bathymetry - Earths rotation (width of fjord and stratification) - Ice formation - Fresh water input (river runoff, glacial melt, sea ice melting) - Tides
Describe Arctic fjords during summer:
A three layer structure can be found during summer when the fjord is free of ice. In this period wind will be the dominant mixing force.
Describe Arctic fjords during autumn:
In autumn the water temperature decreases and this together with stronger wind leads to deepening of the mixed layer through thermal convection. The result is a layer of cold and fresher water over a layer of more saline bottom water.
Since this water is locally produced it is termed Local Water. How deep the thermal convection can reach depends on the density of the deeper water.
Describe Artic Fjords during Winter:
Describe Arctic Fjords during spring:
Describe the Three different winter types:
Type 1 (DEEP): cooling and sea ice formation with thermal and haline convection to the bottom of the fjord Type 2 (INTERMEDIATE): inflow of AW in the lower layer of the fjord -\> cooling and sea ice formation with thermal and haline convection down to the AW layer Type 3 (OPEN): inflow of AW all the way to the surface, only thermal convection of cooled AW all the way to the bottom producing VERY dense Winter Water
Explain the different water masses in the Arctic:
External, Local and Mixed
External Atlantic Water (AW): T \> 3°C; S \> 34.9 Arctic Water (ArW): -1.5 \< T \< 1.0; 34.3 \< S \< 34.8
Local: Surface Water (SW): T \> 1°C; S \> 34 Local Water (LW): T \< 1°C Winter Cooled Water (WCW): T \< -0.5°C; S \> 34.4
Mixed Transformed AW (TAW): T \> 1°C; S \> 34.7 Intermediate Water (IW): T \> 1°C; 34 \< S \< 34.7
Explain the local/internal water masses and how they are formed
Explan the formation of TAW
Explain the formation of IW
Which currents takes place in the fjord-shelf exchange outside West-Spitsbergen current?
Explain the corrialation between Shelf-fjord exchange and sea ice formation
The connection between advection of AW/TAW and the density of LW/WCW
Fjord-shelf exchange connected to the dirrerences in densities of water at the shelf and in the fjord
Freshwater in a fjord:
- What do we mean by freshwater?
- What are the freshwater sources that we have to consider?
- Water with zero or very low salinity
- – Precipitation – River runoff – Glacial ablation/calving – Sea ice meltwater
How would you classify the different fjords of Isfjorden in terms of batymetry?
Isfjorden: no sill, but have some depressions. have 2 “basins” within; the outer and the inner basin
Billefjorden: typical sill-fjord. Cold water in the summer as well as the winter because of the sill –> trapping cold water.
Nordfjorden: no sill
Dicksonfjorden: has a shallow sill
Explain how the rotation of the earth can affect the flow inside the fjord
Dependent on the latitude, stratification and the ewidth of the fjord.Can canculate the INETRNAL rossby radius.
R = c/f
If the R is less than the width, then the fjord is broad. We will expect the flow along the right shoreline, (steered to the right).
Explain how the wind can affect the circulation INSIDE the fjord:
Explain how the Wind outside the fjord affects the circulation in the fjord:
Circulation in the top layer of the fjord is often dominated by wind forcing which gives rise to EKMAN TRANSPORT.
The flow of the surface layer is determined by whether the wind is steered in-fjord or out-fjord. Result: Downwelling / upwelling along the coast
Explain the three layer-structure that is typically found inside the fjord:
- The upper layer typically consists of fresh water from terrestrial runoff.
- The intermediate layer tends to consist of water masses advected from outside of the fjord and mixed with water from the fjord.
- The deepest layer must be denser than the overlying layers and has a generally higher salinity.
