README

This document describes the contents of this data repository which contains the data products used in "Comparing observations and parameterizations of ice-ocean drag through an annual cycle across the Beaufort Sea", by Brenner et al., (submitted). These data were collected as part of the Stratified Ocean Dynamics of the Arctic (SODA) project; more information about the project can be found at apl.uw.edu/soda

Data are included as the following .csv and .mat files (last updated Nov 02, 2020):
- iceMomentum.csv
- iceOceanDragObs.csv
- iceOceanDragParam.csv
- iceGeometryWeekly.csv
- iceGeometryBurst.mat

These data products represent a combination of derived measurements from ERA-5 re-analysis and upward looking Nortek Signature-500 ADCPs deployed on 3 moorings in the Beaufort Sea. General processing and derivations are described in:
	Brenner S.B., L. Rainville, J. Thomson, S. Cole, C. Lee, submitted: Comparing observations and parameterizations of ice-ocean drag through an annual cycle across the Beaufort Sea
Descriptions of each of the files follow.




  iceMomentum.csv

This file contains contains terms calculated as either inputs or outputs of the sea ice momentum balance (eqn. 3 in Brenner et al., submitted). Data are organized in rows that correspond to different moorings and times with comma-delimited fields for each variable. A header row lists variable names as defined below. Unavailable/undefined values are listed as NaN.

Variables:
- mooring     		Name of mooring
- lat         		Latitude [degrees N]
- lon         		Longitude [degrees E]
- mattime     		Time in Matlab serial date format (days from Jan 0, 0000)
- Uo          		Horizontal ocean velocity at 10m ref. depth, expressed in complex notation (u+iv) [m/s]
- Ug          		Geostrophic ocean velocity, expressed in complex notation (u+iv) [m/s]
- Ui          		Ice velocity, expressed in complex notation (u+iv) [m/s]
- Uit         		Ice acceleration, expressed in complex notation (u+iv) [m/s]
- Ua          		Atmospheric (wind) velocity at 10m from ERA-5 re-analysis, expressed in complex notation (u+iv) [m/s]
- iceDraft    		Ice draft [m]
- iceConc     		Ice concentration from ERA-5 re-analysis [unitless]
- f           		Coriolis parameter [radians/s]
- rhoA        		Surface air density from ERA-5 re-analysis [kg/m3]
- rhoW        		Water density (assumed value) [kg/m3]
- WF          		Wind factor: abs(Ui/Ua) [unitless]
- Cai         		Atmosphere-ice drag coefficient (calculated based in ice concentration) [unitless]
- tauAI       		Atmosphere-ice stress, expressed in complex notation (tx+i*ty)  [Pa]
- tauIO       		Ice-ocean stress, expressed in complex notation (tx+i*ty)  [Pa]
- UStar       		Ice-ocean friction velocity, expressed in complex notation (u+iv)  [m/s]
- betaRef     		Turning angle at 10m ref. depth [radians]
- betaG       		Turning angle with respect to the Geostrophic flow [radians]

Notes:
- All horizontal vector quantities (e.g., velocity, stress) are expressed in complex notation, so the real component is the eastward vector component and the imaginary component is the northward vector component.
- Derived tauIO, UStar, betaRef, and betaG are calculated for all times, but these values are only valid if sea ice is in free drift (i.e., internal ice stress is negligible). It is the responsibility of users of these data to choose appropriate filtering of those values (e.g., based on wind factor).




  iceOceanDragObs.csv

This file contains contains "observed" ice-ocean drag coefficient results determined based on weekly linear regression of calculated friction velocity-squared and observed relative velocity-squared (data from iceMomentum.csv). Data are organized in rows that correspond to different moorings and times with comma-delimited fields for each variable measured. A header row lists variable names (as defined below). Unavailable/undefined values are listed as NaN.

Variables:
- mooring     		Name of mooring
- mattime     		Time in Matlab serial date format (days from Jan 0, 0000)
- Cio         		Ice-ocean drag coefficient [unitless]
- CioUnc      		95%-confidence uncertainty in the ice-ocean drag coefficient [unitless]
- r2          		Coefficient of determination, r-squared, from weekly regressions [unitless]




  iceOceanDragParam.csv

This file contains contains parameterized ice-ocean drag coefficient results determined based on sea ice geometry statistics. Data are organized in rows that correspond to different moorings, parameterization schemes, and times with comma-delimited fields for each variable. A header row lists variable names (as defined below). Unavailable/undefined values are listed as NaN.


Variables:
- mooring     		Name of mooring
- scheme      		Name of parameterization scheme
- mattime     		Time in Matlab serial date format (days from Jan 0, 0000)
- Cf          		Floe-edge drag (eqn. 8a) [unitless]
- Ck          		Keel drag (eqn. 8b) [unitless]
- Cs          		Skin drag (eqn. 8c) [unitless]
- Cio         		Ice-ocean drag coefficient [unitless]

Notes:
- Parameterization scheme names correspond to Table 2 in Brenner et al. (submitted).:
... L11:    L11
... T14I:   T14(I)
... T14II:  T14(II)
... T14III: T14(III)




  iceGeometryWeekly.csv

This file contains contains weekly sea ice geometry statistics derived from "burst" sampling measurements (used to calculate the parameterized drag coefficients in iceOceanDragParam.csv). Data are organized in rows that correspond to different moorings and times with comma-delimited fields for each variable. A header row lists variable names (as defined below). Unavailable/undefined values are listed as NaN.

Variables:
- mooring           	Name of mooring
- mattime           	Time in Matlab serial date format (days from Jan 0, 0000)
- burstDist         	Total along-burst ice distance measured [m]
- iceBurstPercent   	Proportion of bursts within the window that were registered as ice [unitless]
- A                 	Local ice concentration [unitless]
- dlvl              	Draft of level ice [m]
- ll                	Lead length (mean length between floes) [m]
- lf                	Mean floe chord length [m]
- hkTot             	Mean total keel depth [m]
- hkRel             	Mean relative keel depth [m]
- hkMax             	Relative depth of largest keel observed within the window [m]
- lk                	Mean keel spacing [m]
- vRdg              	Total volume of ridged ice per unit width [m^2]
- aRdg              	Total area of ridged ice per unit width [m]
- ai                	Total area of ice per unit width [m]

Notes:
- Refer to Figure 1 in Brenner et al. (submitted) for a schematic of sea ice geometry definitions.




  iceGeometryBurst.mat

This file contains a Matlab-readable structure array named "iceGeometry" that contains derived geometric measurements from individual bursts at all three mooring locations (used to derive the statistics in iceGeometryWeekly.csv). Each element of the structure array corresponds to one individual burst measurement, with fields containing different variable measurements or nested structures (as defined below). Unavailable/undefined values are listed as NaN.

Fields:
- mooring         	Name of mooring
- burstTime       	Time in Matlab serial date format (days from Jan 0, 0000)
- isIce           	Binary operator defining each burst as ice (1) or open water (0)
- lfVar           	Low-frequency variance [m^2]
- hfVar           	High-frequency variance [m^2]
- iceSpeed        	Average ice speed during burst [m/s]
- burstDistance		Along-burst ice distance measured [m]
- leads
  └─ leadPercentBurst   Proportion of burst defined as lead/open water [unitless]
  └─ numLeads           Number of leads found in the burst [#]
- levelIce
  └─ draft              Level ice draft [m]
  └─ lvlPercentBurst    Proportion of burst defined as level ice [unitless]
  └─ volume             Volume of level ice per unit width [m^2]
- ridgedIce
  └─ ridgedPercentBurst Proportion of burst defined as ridged ice [unitless]
  └─ volume             Volume of level ice per unit width [m^2]
- numKeels        	Number of keels found in the burst [#]
- keelHeightsTot  	A vector containing all of the total keep depths defined for that burst [m]
- keelHeightsRel  	A vector containing all of the relative keep depths defined for that burst [m]

Notes:
- Refer to Figure 1 in Brenner et al. (submitted) for a schematic of sea ice geometry definitions.

Examples of usage in Matlab:
1. Find the total depth of the deepest ice keel:
  >> load('iceGeometryBurst.mat');
  >> biggestKeel = max( [iceGeometry.keelHeightsTot] );
2. Find the total depth of the deepest ice keel at the SODA_A mooring:
  >> load('iceGeometryBurst.mat');
  >> ind = strcmp([iceGeometry.mooring],"SODA_A");
  >> biggestKeel = max( [iceGeometry(ind).keelHeightsTot] );
3. Plot a timeseries of level ice draft at the SODA_A mooring:
  >> load('iceGeometryBurst.mat');
  >> ind = strcmp([iceGeometry.mooring],"SODA_A");
  >> time = [iceGeometry(ind).burstTime];
  >> draft = arrayfun( @(S) [S.levelIce.draft], iceGeometry(ind) );
  >> plot( time, draft,'.');
