Density Ratios and Heat Flux within the Beaufort Sea Utilizing WHOI Ice-Tethered Profiler Data By LCDR Greg Caro

Motivation http://www.whoi.edu/oceanus/viewArticle.do?id=33006

Motivation Determine typical density ratios within the Beaufort Gyre in order to model vertical heat fluxes within the thermocline. Is the warming of the Atlantic Water layer significant enough to effect the melting rate of the Arctic sea ice cover?

Motivation Turner (1973) describes double-diffusive convection as a phenomenon that occurs when there are gradients of two or more properties with different molecular diffusivities. This difference leads to net density distribution which decreases upwards with the presence of instability within the concentration.

Motivation Alpha is the thermal expansion coefficient (1) Alpha is the thermal expansion coefficient Beta is the saline contraction coefficient Double Diffusion can occur when density ratio is greater than 1. Heat fluxes increase as density ratio approaches 1

Motivation Cp is the specific heat capacity K is thermal diffusivity (2) Marmorino and Caldwell, 1976 Cp is the specific heat capacity K is thermal diffusivity Pr is the prandtl number (kinimatic vicscosity/K) dθ is the background temperature gradient

Profiler Description http://www.whoi.edu/oceanus/viewArticle.do?id=33006

Measuring Capability Measures Conductivity, Temperature and Depth at 1 Hz sample rate Profile design speed of .25 m/s yielding a nominal vertical resolution of 25 cm Iridium satellite communication Designed to collect 1500 profiles in upper 750m 1.5 million meter range 3 year life or ice floe life http://www.whoi.edu/fileserver.do?id=35804&pt=2&p=41486

Data Description LEVEL 1 RAW DATA The raw sensor and engineering data acquired by the ITP profilers are uploaded after the completion of each one-way traverse. The binary data are unpacked and reformatted into Matlab, one file per profile, called raw####.mat, where #### is the profile number. http://www.whoi.edu/fileserver.do?id=35804&pt=2&p=41486

Data Description LEVEL 2 REAL TIME DATA At this level of processing, the location data are filtered and interpolated to the start times of each profile, while the scientific and engineering data are averaged in 2-db bins and salinity is derived from bin-averaged pressure, temperature and conductivity. No sensor response corrections, calibrations or editing are applied at this stage (beyond the internal sensor calibrations applied in the CTD instruments).. http://www.whoi.edu/fileserver.do?id=35804&pt=2&p=41486

Data Description LEVEL 3 ARCHIVE DATA This form of ITP data represent our best estimates of the ocean properties derived from the sensor observations. These data have had sensor response corrections applied, regional conductivity adjustments made based on historical hydrographic data, and edits performed. Level 3 data products are derived for each ITP system after its mission has ended. http://www.whoi.edu/fileserver.do?id=35804&pt=2&p=41486

ITP Track http://www.whoi.edu/page.do?pid=23099

ITP Track 2 1 3 5 2 2 Start * End O

T-S Profiles Depth, dbar Depth, dbar Potential Temp, deg C Salinity ITP 2 244 profiles Depth, dbar Depth, dbar Potential Temp, deg C Salinity

Thermohaline Staircase ITP 2 244 profiles Every 20th Depth, dbar Potential Temp, deg C

Thermohaline Staircase ITP 2 244 profiles Every 50th Depth, dbar Potential Temp, deg C

Thermohaline Staircase ITP 2 244 profiles Every 50th Depth, dbar Potential Temp, deg C

Calculation Methodology Depth, dbar Potential Temp, deg C Identified Steps (|dT/dZ|=max) Difference of T and S at midpoint of each step Used Matlab seawater toolbox to calculate alpha and beta (1)

Results ITP 1 Number of occurrences Density Ratio Mean = 4.8676 +/- 1.7241    Median = 4.5766      

Results ITP 2 Number of occurrences Density Ratio Mean = 4.8059 +/- 1.5182 Median =   4.6655         

Results ITP 3 Number of occurrences Density Ratio Mean = 5.4247 +/- 1.7001    Median = 5.2203      

Results ITP 5 Number of occurrences Density Ratio Mean = 4.5915 +/- 1.3315    Median =   4.4726    

Results Profiler Heat Flux, watts/m^2 ITP 1 0.2765 ITP 2 0.2827 ITP 3 (2) Marmorino and Caldwell, 1976 Profiler Heat Flux, watts/m^2 ITP 1 0.2765 ITP 2 0.2827 ITP 3 0.2384 ITP 5 0.2810

Questions http://www.phys.ocean.dal.ca/programs/doubdiff/demos/Layerformation.html