1: Arctic Fjords

Question 1

The fjords circulation is dependent on

Answer 1

• Wind forcing - Bathymetry - Earths rotation (width of fjord and stratification) - Ice formation - Fresh water input (river runoff, glacial melt, sea ice melting) - Tides

Question 2

Describe Arctic fjords during summer:

Answer 2

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.

Question 3

Describe Arctic fjords during autumn:

Answer 3

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.

Question 4

Describe Artic Fjords during Winter:

Answer 4

Question 5

Describe Arctic Fjords during spring:

Answer 5

Question 6

Describe the Three different winter types:

Answer 6

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

Question 7

Explain the different water masses in the Arctic:
External, Local and Mixed

Answer 7

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

Question 8

Explain the local/internal water masses and how they are formed

Answer 8

Question 9

Explan the formation of TAW

Answer 9

Question 10

Explain the formation of IW

Answer 10

Question 11

Which currents takes place in the fjord-shelf exchange outside West-Spitsbergen current?

Answer 11

Question 12

Explain the corrialation between Shelf-fjord exchange and sea ice formation

Answer 12

Question 13

The connection between advection of AW/TAW and the density of LW/WCW

Answer 13

Question 14

Fjord-shelf exchange connected to the dirrerences in densities of water at the shelf and in the fjord

Answer 14

Question 15

Freshwater in a fjord:

1. What do we mean by freshwater?
2. What are the freshwater sources that we have to consider?

Answer 15

1. Water with zero or very low salinity
2. – Precipitation – River runoff – Glacial ablation/calving – Sea ice meltwater

Question 16

How would you classify the different fjords of Isfjorden in terms of batymetry?

Answer 16

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

Question 17

Explain how the rotation of the earth can affect the flow inside the fjord

Answer 17

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).

Question 18

Explain how the wind can affect the circulation INSIDE the fjord:

Explain how the Wind outside the fjord affects the circulation in the fjord:

Answer 18

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

Question 19

Explain the three layer-structure that is typically found inside the fjord:

Answer 19

• 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.