class: center, middle, inverse, title-slide # Changes in the Seasonality and Duration of Upwelling off the U.S. Pacific Northwest ## Using an Automatic Detection Method ### Howard Baek, Elizabeth Eli Holmes ### 2021-10-09 --- # Agenda 1. Introduction to Upwelling & Importance of Upwelling 2. Automatic Detection Method: Algorithm for Detecting Upwelling 3. Our Automatic Detection Method (ADM) 4. Relationship of Upwelling Index with ADM 5. Results from our ADM 6. Conclusion --- # The Upwelling Process ![](https://images.squarespace-cdn.com/content/v1/59149d9a6a49631b4f066334/1583205905877-JQM3GUSXFKEPKG4JIMXB/UpwellingDetailed_Gif.gif?format=1000w) --- # The Importance of Upwelling .pull-left[ ![](https://media.nationalgeographic.org/assets/photos/000/278/27837.jpg) ] .pull-right[ - Brings nutrient rich water to the surface - Supplies nutrition necessary for biological productivity - Coastal upwelling regions contribute roughly 50 percent of the world’s fisheries landings ] --- # Dataset .pull-left[ ![](https://user-images.githubusercontent.com/50791792/128484169-e064642f-33be-4b3a-9058-eac7240bc864.png) ] .pull-right[ - Daily Optimum Interpolation (OI) SST - 4 columns: time, latitude, longitude, and SST (sea surface temperature) - **SST** is defined as the water temperature close to the ocean’s surface. ] --- # Past Work in Detecting Upwelling .pull-left[ Gidhagen (1987): _Abnormal temperature drop of at least 2°C compared to earlier and surrounding measurements_ <img src="presentation-images/gidhagen-paper.png" width="1392" /> ] -- .pull-right[ Lehmann, Myrberg, and Höflich (2012): _Temperature difference for each individual pixel from the zonal mean temperature, for every pixel line_ <img src="presentation-images/lehman-paper.png" width="1461" /> ] --- # Our Automatic Detection Method (ADM) * Looks at each latitude and finds the SST of the coastal water (water closest to land) and the SST of water 2 and 3 degrees away from land (_SST coast 2_ and _SST coast 3_) * Computes two differences: the difference in SST between the coastal water and _SST coast 2_ and the difference in SST between the coastal water and _SST coast 3_. * Checks if either of these two differences exceeds a threshold of 2°C + If it does, we indicate **upwelling** at the specific latitude + If not, we indicate **non-upwelling**. --- # Our Automatic Detection Method (ADM) <img src="http://insidethetv.rbind.io/post/2021-09-10-automatic-detection-of-upwelling/images/stamen-map-final.png" height="520px" /> --- # Exploration of Upwelling Percentage > Upwelling percentage: Proportion of days over relevant timeframe in a figure that are categorized as upwelling by our automatic detection method. --- # Exploration of Upwelling Percentage (I) ![](http://insidethetv.rbind.io/post/2021-09-10-automatic-detection-of-upwelling/images/heatmap-upwelling-percentage-decade.png) --- # Exploration of Upwelling Percentage (II) ![](http://insidethetv.rbind.io/post/2021-09-10-automatic-detection-of-upwelling/images/heatmap-upwelling-percentage-month-year.png) --- # Exploration of Upwelling Percentage (III) ![](http://insidethetv.rbind.io/post/2021-09-10-automatic-detection-of-upwelling/images/heatmap-upwelling-percentage-latitude-bins.png) --- # Exploration of Upwelling Percentage (IV) ![](http://insidethetv.rbind.io/post/2021-09-10-automatic-detection-of-upwelling/images/heatmap-upwelling-percentage-latitude-month.png) --- # Changes in Upwelling Phenology ![](http://insidethetv.rbind.io/post/2021-09-10-automatic-detection-of-upwelling/images/first-day-upwelling.png) --- # Changes in Upwelling Duration <img src="http://insidethetv.rbind.io/post/2021-09-10-automatic-detection-of-upwelling/images/duration-upwelling.png" height="520px" /> --- # Discussion of ADM - _Naidu et al. (1999): Studied monsoonal upwelling along the West / East coasts of India using monthly mean local temperature anomaly (LTA)_ -- - _Smitha et al. (2008): Also used LTA as an upwelling index_ -- - _Holmes et al.(2021): Used SST differential to study upwelling in the Southeast Arabian Sea_ --- # Discussion of Strength of Upwelling - _Hickey and Banas (2003): In general, the strength and duration of upwelling increases to the south in the PNW_ -- - _Bograd et al. (2009): Developed a set of indexes to understand the coastal upwelling in the California Current large marine ecosystem (CCLME)_ --- # Conclusion 1. Southern latitudes (40°N ~ 45°N) had higher upwelling percentages than Northern latitudes (45°N ~ 50°N) 2. Found the upwelling months (upwelling percentage higher than 25%) to be from June to October and the non-upwelling months from November to May 3. Upwelling started later for northern latitudes (45.0°N to 50.0°N) around August and September. 4. Northern latitudes had shorter duration of upwelling than the southern latitudes. --- # Thank You for listening! ![](https://media4.giphy.com/media/F0NNF3rFvE13mRrzDz/giphy.gif?cid=ecf05e47vvvtedb1mpzf2w3nv03yvppayhmsfxk8rso0brss&rid=giphy.gif&ct=g) <br> ### Contact: howardba@uw.edu