Objectives Background Methods Conclusion

Arctic Climate Change: Ocean Mixing Rachel Patteson International Arctic Research Center

Objectives

Results

Using statistical analysis for the first test at 50m depth level, all 8 mooring locations resulted in summaries of weak correlations (Fig. 5). The average correlations between ocean current and wind speed rested around 0.20 for most moorings. Since all presented low correlation values, there was no need to continue further tests at deeper depth levels – since the effect of wind decreases at deeper depths. The cloudiness in Fig. 6 is an example of very low correlations seen in most moorings.

1. Investigate the impact of surface winds on Arctic Ocean mixing. 2. Use data from 8 mooring Laptev Sea sites and test correlations between surface wind speed and ocean currents. 3. Determine factors that contribute to shoaling of warm Atlantic water.

Background

Fig.1. 4 Layers of the Arctic Ocean. Red and blue indicate different zones. Left column is temperature and right is salinity.

Conclusion

The crucial understanding is the Arctic ocean water is losing its basic stratifcation features, altering certain components of the Arctic Ocean. The constant melting of sea ice due to warming penetration predicts a new Arctic climate. The final findings suggests there is another dominating factor at play influencing the shoaling of Atlantic Water : Topography (Fig.8.).

The Arctic Ocean has 4 main depth profiles (Fig. 1). SML mixes due to brine rejection from ice growth. The CHL originally works as a barrier between the saltier water below and fresher water above and resists the AW (source of heat) from penetrating through. Heat loss from AW through the CHL can be due to eddy stirring, advection, and other unknown processes. Problem: The Eastern Eurasian Basin (Laptev Sea, Fig. 3) is showing weaker stratification properties, allowing more heat to penetrate the lower part of sea ice, causing melting from the bottom up. The question is what is causing the weaker stratification. I predicted weaker stratification in the CHL (up to 70m) is due to mixing from increased storm events. Original observation shown in Fig. 2.

Methods 1. Test the correlation between wind surface speed and ocean currents at 50-meter depth level. 2. If correlation is above 0.60 for most mooring sites, then test at deeper depths levels. • Data collected from 8 mooring locations in the Eurasian Basin of the Arctic Ocean (Fig. 3). • 2-year ocean current measurements taken with Acoustic Current Profilers and Wind Speed from ERA-interim

Fig.2. Mixing in the top graph correlating to storm events in the bottom (arrow).

Fig.8. Topography of Laptev Sea slope area and locations of Mooring M1-M6b.

Fig.5. Results for all 8 mooring sites with raw correlations. Blue represents ocean currents; red is wind speed.

Fig.3 Arctic Ocean Circulation, detailing laptev sea where data was taken (circled).

I then tested for specific storm events (wind speeds over 15 m/s). I found high correlations for most events (above 0.60). The high correlations may have been a coincidence, so I used the 5-sigma standard test to determine statistical significance of the ocean current magnitude at storm events (Fig. 7). I found there were no moorings with magnitudes over 4 or 5 sigmas.

Fig.6 Scatterplot of Mooring M11. Shows low correlation between ocean currents and wind speed. Fig.4. Schematic of moorings.

Fig.7 Mooring M3e storm event (between vertical bars). 5 sigmas shown by the dotted lines. The blue line indicates ocean current magnitude.

My conclusion assumes that topography may have a bigger influence on currents and mixing than we thought. The ocean currents are not at all corresponding to surface winds. Mixing in the Laptev Sea area may ultimately be due to density differences and topography, and thus more research will need to be done.