Hypoxia in the Gulf of Mexico: Data Collection Methods, Causes, and Future Planning

Introduction
Hypoxia refers to the condition of low dissolved oxygen content in a body of water (Rabalais, Turner, & Wiseman, 2002b). The level of oxygen at which a body of water would be described as hypoxic is not universally defined or accepted, but is most often classified within the general range of 3.0 to 0.2 ml 1‐1 (Rabalais et al., 2002b). Hypoxia develops when a stratified water column, with separation of the bottom and top water layers due to differing temperatures, salinity, or both, experiences decomposition of organic matter to such an extent that the bottom water oxygen levels are reduced (Rabalais et al., 2002b).
This condition occurs in the Gulf of Mexico on a large scale, with the hypoxic area exceeding 20,000 square kilometers (Justic, Rabalais, & Turner, 2003). This makes it the second largest hypoxic zone in area in the world, exceeded only by the Baltic basins at approximately 70,000 square kilometers (Rabalais, Turner, & Scavia, 2002a). A level of oxygen of 2 milligrams per liter or less is used as the operational definition of hypoxia specific to the Gulf of Mexico, as no shrimp or demersal fish are caught by trawlers in that oxygen range (Rabalais et al., 2002a). Hypoxia was initially reported in the Gulf of Mexico in the early 1970s, and systematic mapping and comprehensive assessment began in 1985 (Rabalais et al., 2002a).
The Gulf of Mexico is fed by both the Mississippi and Atchafalaya Rivers, and the increased levels of nitrogen and declining water quality of these sources has been blamed for the growth of the hypoxic zone (Donner, Kucharik, & Foley, 2004). The overlapping of this zone with commercially important fishing zones combined with the increasing environmental concern have made this a highly researched area of study, with an emphasis on potential human impact from nitrogen loading (Donner et al., 2004). Several “Action Plans for Reducing, Mitigating, and Controlling Hypoxia in the Northern Gulf of Mexico” have been created and endorsed by both state and federal governments (Rabalais et al, 2002a).
Mapping the size of Gulf hypoxia

Since 1985, the Gulf of Mexico has been mapped annually, usually in midsummer between the middle of July and August, in order to determine the extent of the hypoxic zone (Rabalais et al., 2002a). Results of oxygen testing of water samples show that the hypoxic water mass reaches in a westerly direction from the Mississippi River Delta, extending across the Louisiana Shelf, and within a ranging distance from the upper Texas Coast(Rabalais et al., 2002a). Hypoxic conditions were found to exist at depths of up to 60 meters, but most often between 5 and 30 meters (Rabalais et al., 2002b). The size has changed over the surveyed time, ranging between 8,000 to 9,000 square kilometers from 1985 and 1992, and after the Great Mississippi Flood increasing to between 16,000 and 21,000 square kilometers from 1993 and 2001. (Rabalais et al., 2002a).
More frequent sampling was conducted in order to determine the oxygen levels at different times during the year, and results indicated that hypoxic levels below the pycnocline existed from the end of February through until October. (Rabalais et al., 2002b). Almost continuously present from the middle of May through September, hypoxia presence was inconsistent through March, April, and May, and was the most demonstrably present and severe through the summer months of June, July, and August (Rabalais et al., 2002b).

Sediment denitrification

The increasing zone of hypoxia in the Gulf of Mexico is largely attributed to the increased decomposition of organic matter due to the accelerated rate of primary production, found especially in the summer months (Childs, Rabalais, Turner, & Proctor, 2002). Childs et al. (2002) state that the increased production is driven mainly by the heightened input of inorganic nitrogen, primarily from the Mississippi River. Nitrate and nitrite can be reduced to nitrous oxide or dinitrogen through denitrification, a form of anaerobic microbial respiration, forming a sink for bioavailable nitrogen (Childs et al., 2002). The facultative anaerobes that perform this process only start to denitrify when nitrogen oxides are present and oxygen concentration is low, however at very low oxygen levels nitrate could reduce to ammonia as opposed to undergoing denitrification (Childs et al., 2002).
Childs et al. (2002) performed a study to find sediment denitrification rates, measured at 7 different stations along the Louisiana Shelf in 1999 at the peak of the hypoxic season, in order to compare with reported rates from other areas and contemporaneous water quality data. To conduct this study, the bottom water of the Gulf of Mexico was surveyed from the RV ‘Pelican’ on a transect cruise covering more than 20,000 km2 and 83 stations (Childs et al., 2002). Collections were made at each of these stations of water samples and hydrographic data, including pH, temperature, conductivity, dissolved oxygen levels, salinity, fluorescence, percent of light transmitted, and depth (Childs et al., 2002). Bottom water and midwater samples were retrieved using 5 1 Niskin bottles, and surface water level samples were collected simply using buckets (Childs et al., 2002). Intact sediment cores were taken from each of seven specific stations using a boxcoring device (Childs et al., 2002).
The water samples were then incubated, anaerobically to prevent contamination, in 160ml serum bottles (Childs et al., 2002). Included was a head space which contained a combination of nitrogen gas and ethyne gas, which was then transferred to 10ml Vacutainers and analyzed using a Shimadzu GC‐8A gas chromatograph to determine the linearity of N2O production (Childs et al., 2002). The box core samples were sub‐cored using butyrate cores that were 5cm in diameter, with a water layer being kept over the surface of the sediment in order to reduce oxygenation before analysis (Childs et al., 2002).
The results of the analysis found that the hypoxic zone in the summer of 1999 spanned over 20,000 km2, and that denitrification rates varied depending on the concentration of dissolved oxygen (Childs et al., 2002). As expected, the highest rates of denitrification occurred where the dissolved oxygen concentration ranged between 1 and 3 mg l‐1, and the lowest rates occurred where the dissolved oxygen concentration was 5.1 mg l‐1 (Childs et al., 2002). However, when the dissolved oxygen levels dropped below 1 mg l‐1, the denitrification rates were found to be about half of the rates found at levels above 1 mg l‐1 (Childs et al., 2002). The rates overall were found to be at the low end on the scale of rates reported from other systems, which was somewhat unexpected as hypoxic conditions of low oxygen levels, high carbon levels, and high amounts of nitrate should be ideal for denitrification (Childs et al., 2002). The observed rates do vary significantly and the highest rates were found in shallow waters near shore and in the more freshwater environments, whereas the other areas (likely in situ denitrification) could be lower due to the fact that Childs et al. (2002) measured the maximum potential denitrification capability of the sediment, which is not consistent among all studies.
Overall, the data collected by Childs et al. (2002) suggested a positive feedback loop existing between the severity of hypoxia and the duration of presence of fixed nitrogen, resulting in exacerbating hypoxic conditions. As the process of denitrification was suppressed under severe hypoxia, this would effectively increase the amount of bioavailable nitrogen present in the water, which is thereby associated with an increase in primary productivity‐ a factor leading to the original development of the hypoxic zone(Childs et al., 2002).

Contributing Factors

Justic et al. (2003) collected data and ran a mathematical model in order to determine correlation of hypoxia with concentration of nitrate and ambient water temperatures, specific to the Mississippi River discharge. The Mississippi River Watershed/ Gulf of Mexico Hypoxia Task Force has established a goal to reduce the area of the hypoxic zone to less than 5000 km2 by 2015, with a proposed action plan requiring a decrease of 30% in nitrogen flux (Justic et al., 2003). Justic et al. (2003) ran models in order to determine whether this would be an adequate target in order to meet that goal,and how the river discharge would be affected by the climactic impact of global warming.
Through the use of a two‐box modeling system, assuming uniform properties for both layers below and above the pycnocline, Justic et al. (2003) used oxygen flux, oxygen concentration, nitrate flux, and numerous other variables to predict the relationship between nitrate concentration, temperature, and hypoxia. The results of the study indicate that the hypoxic conditions in the Gulf of Mexico are very sensitive to variations in river discharge, nitrate flux, and water temperatures, and indicate that a nitrogen flux decrease of 30% from the Mississippi River may not actually be enough in order to meet the task force goal (Justic et al., 2003). For example, a 30% decrease in such flux was predicted to result in a 37 % decrease in the frequency of hypoxia, however an increase in discharge by only 27% was found to produce the same magnitude of increase of hypoxia under some climactic change scenarios. (Justic et al., 2003). More research and modeling would be required in order to more conclusively determine the magnitude of the correlation, but the study performed by Justic et al. (2003) did provide strong evidence for simply the existence of a correlation.

Effect of Nitrogen Fertilizer

A study by Donner et al. (2004) examined how agricultural practices, combined with climate influences, affect the input of nitrogen into the Mississippi River Basin and therefore the Gulf. A modeling system called HYDRA uses the IBIS model predicted runoff, surface runoff, groundwater drainage, and nitrate leaching in order to simulate river discharge and nitrate export, which has been widely blamed in popular media for the growth of the hypoxic zone in the Gulf of Mexico (Donner et al., 2004). This study was also the first time that a process‐based and dynamic modeling system had been used to predict and simulate the combined influence of the use of fertilizer, land management, and climate on the nitrogen cycle and the export into the river basin (Donner et al., 2004). The simulations from the model indicated that the factors leading to the doubling of nitrate export into the Mississippi River since 1960 can be attributed to an increase in fertilizer use, especially on maize, the recent increase in popularity of soy and the subsequent expansion of soybean cultivation, and an increase in runoff into the basin (Donner et al., 2004). Donner et al. (2004) presented findings that suggest that up to 90% of the nitrate found in the river could be attributed to fertilized crops, with the majority appearing to originate from an area known as the “Corn Belt,” which is a stretch of land across Iowa, Illinois, and Indiana.

Historical Analysis

The Gulf of Mexico has been the focus of observation and studies for over 30 years, as early as the 1970s as indicated by attached Table 1 (Rabalais et al., 2002a). As previously mentioned, the hypoxic zone has been increasing, and more largely affecting commercial fisheries and economics, and combined with the growing environmental concern the amount and intensity of studies conducted on this area have also increased within the last several years (Rabalais et al., 2002a). In 1990, continuously recording (at 15 minute intervals) oxygen meters were deployed at a 20m depth along Terrebonne Bay in the Gulf (Rabalais et al., 2002b). Since this time, the emerging pattern shows a gradual decline of oxygen concentrations in bottom water during spring and summer, with persistent hypoxia for extended periods from May through September, and subsequent wind mixing in the fall that is sufficient to prevent bottom water hypoxia for prolonged periods of time (Rabalais et al., 2002b). As water column data before the 1970’s is not available, sediment records for paleoindicators of long term transitions relating to concentrations beneath the Mississippi River, specifically oxygen conditions, can be used (Rabalais et al., 2002b). Sediment cores from both within and beyond the hypoxic region were found to contain both biological and chemical remnants that can reflect the conditions of both the bottom and surface waters at the time of sediment deposition, which can therefore provide evidence of changes that occurred as long as a century ago (Rabalais et al., 2002b). The sediment cores analyzed by Rabalais et al. (2002b) indicate, using accumulated amounts of diatom remains and marine‐origin carbon, an overall increase of hypoxic conditions has occurred since the turn of the century, and an increase in severity since the 1950s, when the nitrate flux to the Gulf of Mexico from the Mississippi River tripled. Since no significant increase in organic carbon or silica in rivers since 1950 has been found, it is reasonable to infer that any increase in sediment biologically bound silica since then can be attributed to in situ production of marine diatoms, meaning it is an excellent indicator for this type of production (Rabalais et al., 2002a).
 
Conclusion

With the increase of studies focusing on the situation in the Gulf of Mexico, the numerous conditions that contribute to the worsening situation can be better understood and a more accurate plan of action can be developed. Integrated assessments are being developed and updated, and the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force has published extensive reports in both 2001 and 2008 (Rabalais et al., 2002a). Long term data and paleoindicators both verify and strengthen the relationship between the amount of nitrogen in the Mississippi River and the extent of the Gulf hypoxia (Rabalais, Turner, Sen‐Gupta, Boesch, Chapman, & Murrell 2007). With additional surveys in shelfscale areas, and higher frequency observations at specific and key locations, and other measures of hypoxia including volume and total deficiency of oxygen would increase understanding in the processes that support both the initial formation and the long term maintenance of hypoxia (Rabalais et al. 2007). The recent findings of Rabalais et al. (2007) reinforce the science supporting the increase of hypoxia over the last century and correlation to increased nutrient loading, and support the current Mississippi Task Force Action Plan to focus on reduction of nitrogen addition as a means of reducing hypoxia in the Gulf of Mexico.


Literature Cited
Childs, C. R., Rabalais, N. N., Turner, R. E., & Proctor, L. M. (2002). Sediment denitrification in the Gulf of Mexico zone of hypoxia. Marine Ecology Progress Series, 240, 285‐290
Donner, S. D., Kucharik, C. J., & Foley, J. A. (2004). Impact of changing land use practices on nitrate export by the Mississippi River. Global Biogeochemical Cycles, 18(1), 1.
Justic, D, Rabalais, N. N., & Turner, R. E. (2003). Simulated responses of the Gulf of Mexico hypoxia to variations in climate and anthropogenic nutrient loading. Journal of
Marine Systems, 42(3‐4), 115‐126.
Rabalais, N. N., Turner, R. E., & Scavia, D. (2002a). Beyond science into policy: Gulf of
Mexico hypoxia and the Mississippi River. Bioscience, 52, 129‐142
Rabalais, N. N., Turner, R. E., & Wiseman, W. J. Jr. (2002b). Gulf of Mexico hypoxia, A.K.A. “The Dead Zone”. Annual Review of Ecology and Systematics, 33, 235‐263.
Rabalais, N. N., Turner, R. E., Sen‐Gupta, B. K., Boesch, D. F., Chapman, P., & Murrell, M. C.
(2007). Hypoxia in the northern Gulf of Mexico: Does the science support the plan to
reduce, mitigate, and control hypoxia? Estuaries and Coasts, 30(5), 753‐772.
Gulf of Mexico Sample Sites.

Finding Balance in Education

Teaching in a school setting is only a small part of being an educator. “Educator” is not simply a job that pays the bills, but a way of life, a means by which one expresses herself in the world – an underlying thread that is ever-present in her interactions with others and self. A personal quality that inspires me to become a teacher is my insatiable curiosity. I see opportunities to learn and grow from each moment and encounter in my life. Often these opportunities come from my day to day experiences but many are from my mistakes and failures. By framing my life experiences as learning opportunities and a perpetual evolution toward becoming a more compassionate, whole, aware person, I have learned that it is important to take healthy risks, and that failure is okay. Indeed, I believe that by embracing healthful risks and failures I have learned my emotional, moral, and physical limits and have gained confidence through learning my strengths and embracing/being aware of aspects of myself that are weaker.

Based on this outlook, as an educator one of my goals is to ensure that, along with grasping academic foundations and concepts, students also have equal opportunities to interact with and explore their worlds in various and alternative ways. Through social and emotional education, creative pursuits like art, poetry, and music, physical/health education, exposure to other cultures/ways of life, and outdoor education, students able to make connections across different realms of their lives and apply this knowledge toward a greater (self-)awareness and confidence in their pursuits and expressions.

John Lennon observed, “The more I see, the less I know is for sure.” I believe his observation refers to the idea that the more experiences one is exposed to, the less likely we are to become stuck in specific thought and behavioural patterns. I can personally attest to this through my experiences traveling to different countries and my diversified formal and informal education over the years. By cultivating a sense of curiosity and open-mindedness, we start to see that everything is relative and meaningful, and that asking mindful questions about our inner and outer world is a valuable practice that should be encouraged, in and out of the classroom. Thus, through the caring cultivation of all aspects and skills of the person with gentle guidance from trained and committed educators, students will have an increased opportunity to lay a foundation to develop into balanced, successful, happy adults.

The "Light" Side of Education

Pre-Teaching Thoughts and Experiences
   
    It is mid-February, and I have stepped off the path of continuing post-graduate work in neuroscience onto one toward becoming an elementary school teacher.  I am an in-class volunteer in a grade 4/5 split classroom. The teacher and myself are responsible for approximately thirty children, along with a CEA who works with one. The children are all uniquely wonderful, but the class composition is challenging, with six children who have diagnosed behavioural and/or learning issues. The class consists of children who come from a wide range of home environments and varying degrees of socioeconomic stability, with the catchment area encompassing a trailer park on a First Nation's reserve as well as expensive hillside mansions near a famous winery.
     One day, I was working with a particular child who often has difficulties staying focused and motivated in class. He lives in the nearby trailer park and has low self-esteem, indicated by his withdrawn manner and his frequent self-deprecating comments. That day, he was having difficulty understanding how to tell time on an analog clock. I tried explaining the lesson in as many different and imaginative ways I could come up with, but none of my approaches were clicking with him. I observed his frustration and anxiety mounting, despite my gentle reassurances. Inwardly, I myself was feeling at a loss, as I saw him begin to "shut down". But suddenly, he sat up, his eyes ablaze with comprehension, and he excitedly explained the whole concept back to me! This normally quiet and gloomy boy was all smiles and "high fives"! The light came on in this child, and this was my first "light bulb" moment.

    I have worked in other classrooms before and after this grade 4/5 split, but it was not until my experiences in this particular class that I realized how truly challenging it is to be a teacher. What I had observed made me wonder how it is possible to teach one lesson to such a variety of individuals and personalities. British Columbia public school classes average around 30 children to one teacher, and there is minimal support available to the children (and the teacher) as there appears to be a substantial shortage of CEAs and Learning Assistants in the school district I have volunteered in. Seeing the daily challenges the teacher faced trying to manage this particular group of so many different abilities and personalities made me feel overwhelmed and discouraged. The idea of myself being a teacher became daunting and I started asking myself some honest and probing questions: "Am I the kind of person who is suited to managing the stress and responsibility of guiding the positive development and learning of so many different children?" and "Is this how I really want to dedicate my time and energy?"
    Then I witnessed my first "light bulb" moment. I was reminded that school is not just a place for cognitive growth, but for personal, social, and emotional development as well. While my opportunities to witness moments of sudden light and comprehension can sometimes be painfully few and far between, the possibility of their occurrence motivates and inspires me to be a better teacher and individual. No, not everyone will get the lesson the first, second, or even third time around. Yes, this can be frustrating and discouraging for the teacher, and especially the children. But the role of a teacher is not just to teach and test academic learning. After witnessing the personal empowerment students gain through comprehension and success, I have come to see that the teacher's most important role is to foster and nurture a positive, patient, and compassionate learning environment conducive to holistic growth and light bulb moments for every child.

Hockey Nation -- One Game, Two Visions

Montreal   

    The sentiments of separatism and nationalism among French-speaking Canadians date back centuries.  Yet, even today after decades of so-called compromise and accommodation from the federal government, the fear of absorption into the pre-dominantly anglophone culture of the rest of Canada is still strong.  This fear sometimes manifests itself in the many forms of Quebec nationalism.  Most Quebec Nationalists don’t seem to agree on one form of nationalism, but the top three types seem to be territorial (Quebec sovereignty), linguistic (pro-French language) and ethnic (a pure, Francophone lineage; typically against immigration).  Two examples of particularly active pro-language groups are the Mouvement Quebec Francais and the Mouvement Montreal Francais, who work hard to ensure that the French language and culture remain dominant in the province of Quebec. 
    A recent example of this worry of the regression of French language and culture in Quebec is the french-language protest by the Mouvement Quebec Francais at a NHL Montreal Canadiens game vs the Tampa Lightning in January this year.  Montreal’s hockey team is one of the original 6 hockey teams, making it over a century old.  In its century of existence, it has always been marketed and promoted as the hockey team of French Canada.  It is especially one of the prides of Montreal, one of the oldest cities in Canada, where over 83% of the people have French as their first language. 
    Lately, there has been tension amongst Nationalist Quebecois about the music playing at home Habs games being only in English, and the announcements being bilingual instead of solely French.  This is considered disrespectful by the pro-language groups as Quebec, with 95% of its population speaking French, is officially a Francophone province, not bilingual like the rest of Canada.  There is also some disappointment that French Canada’s team has only 2 players who are actually Francophone. 
    The latest issue concerning the Montreal Habs is that despite the Canadiens’ historical record when it comes to winning Stanley cups, these days they’re actually close to being at the very bottom of the NHL team standings.  As such, their coach was fired, and a new coach was appointed by the manager this past December.  What upset the Quebec Nationalists is the new coach speaks no French, only English.  Pro-French-language protestors were up in arms, and organized a rally outside the Bell Centre at the Habs’ next home game in January versus the Tampa Bay Lightning.  They handed out Quebec flags to those coming to the see the game, chanted “Montreal, en Francais! (Montreal, in French!),” and even brought a dummy resembling the team’s president/owner and put a noose around its neck.  They argued that the team, supposedly being a representative of French Canada, should have a coach who can speak French.  More generally, hockey being “Canada’s Game,” and with Canada officially being a bilingual country, this coach, a representative of Canada’s Game, should at the very least have a grasp of both of Canada’s official languages. 
    The National Hockey League has developed into a privately owned, international organization with players coming from different backgrounds around the globe to play for North American teams.  Teams are no longer recruiting from their own backyards to represent their city; rather, they are buying and trading players internationally in the interest of forming the best team possible in the hopes of winning the most coveted prize in the NHL – the Stanley Cup.  As such, as Canada’s cultural fabric continues to become less of the “1 nation, 2 visions” model of the last century and a half and more a diverse “patchwork quilt” of people and cultures, perhaps Montreal should consider loosening its claim to their Habs as being representative of French Canada, and find pride instead in the hard work of their team’s international roster, doing what it takes to maybe one day bring the Stanley Cup back to Quebec.

Coming Home to Bliss

As I mature, the idea of figuring out where I feel most at home, most able to be me, has become more prominent in my mind.  But the more I consider the idea, the more I realize that, like happiness, that feeling of "home" isn't going to necessarily come from an external source, or physical location.

Everyone of us has experienced those moments of total bliss and contentment, but it seems as soon as those moments slip away, we start striving to get back to that place again and stay there.  Paradoxically, the very act of wanting to hold on to that happy feeling takes it away...

We go through life with these ideas and conceptions of who we are and who we’d like to be (“I’m a woman, a Canadian, I’m ambitious, loving, curious, a student, a daughter...”) and try to align ourselves with positions and people in life that reaffirm these seemingly basic and crucial parts of our identity.  Which is great.  It’s so important to foster our passions and values to elicit positive growth and create beautiful social connections.

But at the same time...all of this is quite limiting.  Imagine, cramming yourself into such a puny box of identity, when you could experience your infinitude instead!  Really, we are not (the sum of) our cognitions, our emotions, our actions, our values...Indeed, these things seem to bury our inner “self”.  Who we really “are” is the *awareness* of all these parts of us.  As soon as everything becomes stripped away, and we are living in a state of pure, present, simple awareness, that’s when I think we attain those ever-elusive flashes of bliss and contentment.

Why would I chase happiness my whole life, when bliss has been here the entire time?  One has the potential to be blissful and content, at any time, always. It just seems most of us simply aren’t ready/able to comprehend this yet.

My proposition: home is whenever/wherever you’re with *you*

Bliss, contentment, nirvana, home, inner peace...whatever you want to call that feeling, that "being," that "place" -- “You may return here once you have fully come to understand that you are always here.” --

Internal Waves Increase Ocean Mixing in the Arctic, Potentially Affecting Global Ocean Circulation and Ecosystems

internal waves in the atmosphere

internal waves forming slicks on the ocean's surface

    

Compared to surface waves, the properties and effects of internal waves in the ocean are still relatively unknown.  These underwater waves have numerous causes and can affect the environment in many different ways. Recent research on the effects of internal waves in the Arctic Ocean sheds light on the profound ways that these swells can affect ocean mixing, circulation, and the planet as a whole.   
    The Arctic Ocean is the smallest and most shallow of the world’s oceans. It is unique in that its water is practically homogenous.  This means its salty, cold, dense deep water qualities are relatively similar to those at the surface.  This is due to several factors.  The shallow Arctic ocean sits mainly in a basin, with only one main channel circulating water in and out of the ocean, called the Fram Strait, located near Greenland (Arctic Ocean Encyclopædia Britannica Online, 2010).  This lack of major circulation potentiates a stable water column, which makes for minimal mixing of the water stratification.  Tides are small, resulting in negligible tidal currents.  The ocean is also covered with ice for the majority of the year.  This  minimizes evaporation by acting as an insulator, maintaining a cold and stable water surface temperature, and reflecting any incoming sunlight.  The ice cover also prevents the wind from mixing the water (Rainville & Woodward, 2009).
    Along with the Kara, Laptev, East Siberian and Barents seas, the Chuchki is one of the five seas that comprise the Arctic Ocean (Arctic Ocean Encyclopædia Britannica Online, 2010).  The Chuchki is north of the Bering Strait, with Alaska on its southeastern edge and Siberia on the southwest.  At its north end is the Arctic continental self.  

Its average depth is only 77 metres, or 250 feet (Arctic Ocean Encyclopædia Britannica Online, 2010).  Because the Arctic Ocean has little circulation, is usually covered with ice, and has a relatively homogeneous water density with little mixing, the water is usually quite calm with little energy output or wave action (Rainville & Woodgate, 2009). However, compared to deeper parts of the ocean, the shallow depth of the Chuchki Sea causes potential internal waves to have more significant effects when it comes to mixing and affecting water circulation (ScienceDaily, March 2010)
    Internal waves occur between waters that are of different salinity/temperature/density.  The differences in density cause the fresher/warmer/less dense water on the surface to behave differently than the typically saltier/colder/denser water below.  The boundary between the layers, or the pycnocline, can move in a wave motion, triggered by tides, underwater topography, or wind (http://earthobservatory.nasa.gov/IOTD/view.php?id=7230).  Internal waves can be visible in some circumstances due to the slicks they sometimes cause on the surface as surface currents are affected.  The crest of the internal wave causes surface particles directly above to spread out, creating a dark, smooth appearance on the surface, while particles and water collect in the troughs of the wave, causing the surface water to be rough and bright in appearance (http://earthobservatory.nasa.gov/IOTD/view.php?id=3586).  Otherwise the sea level remains undisturbed.  Particles in the middle of the water column are moved vertically, though not horizontally, with the passing of each crest and trough of the wave. 

http://www.es.flinders.edu.au/~mattom/IntroOc/lecture10.html




“An internal wave propagating on the interface between two layers. The undisturbed sea level is indicated by the yellow line. Water particles are shown as yellow and magenta dots. Yellow dots sit in the middle of the water column and move only up and down. Magenta dots sit at the top and bottom of the water column and move only in the horizontal.” - Tomczak, M.(2005) Introduction to Physical Oceanography [HTML].

    Rainville & Woodgate (2009) conducted a study in the Chuchki Sea to determine the effects of receding summer ice coverage in the Arctic on internal wave activity and the consequential ocean mixing.  The researchers used two subsurface moorings, one placed at 70 metres below the surface and another, 30 kilometres from the first, at 110 metres below the surface.  Attached to the moorings were devices measuring wind speed, and acoustic devices measuring inertial oscillations in the water as well as ice coverage.  This data was combined with satellite data and ice records from previous years to provide the researchers with as complete a picture as possible on which to compare their experimental observations. 
    Mooring data recorded storms occurring at all times during the year.  The researchers observed that during the winter, when most of the sea was covered by sea ice, there were minimal inertial oscillations under the ice and therefore minimal ocean mixing.  These oscillations were not affected by winds from any of the storms that occurred.  When the ice receded in the summer, inertial oscillations increased.  The melting ice increased water stratification by lowering the density and salinity of surface water as ice water is fresher than ocean water because of the brine rejection that occurs during its formation.  The newly exposed water is now susceptible to internal waves caused by wind mixing.
    At first Rainville and Woodgate speculated that the stronger inertial oscillations and internal wave formation were a result of previously restricted tidal currents now having room to move more freely across underwater topography and manifesting as stronger inertial oscillations and internal waves.  However, data showed that the oscillations and internal wave movements did not correspond with tidal movements and instead were correlated with the recorded storms; As a result, researchers concluded that wind mixing was causing the internal waves.
    Mooring data showed buoyancy frequency (oscillations) beneath the mixed surface layer were positive throughout most the year, meaning that the water column and stratification were stable.  However, during storms, wind caused internal waves.  Inertial oscillations increased when exposed to the wind, and the increased oscillations flowing over the underwater topography create internal waves (Zhang et al., 2008).  These underwater waves create a sort of friction in the boundary between fresher/less dense surface water and the dense deep water, called shear.  The shear caused by the internal waves appears to cause the pycnocline to dissipate, and the mixed surface layer to become deeper (Rainville & Woodgate, 2009).  The eroded pycnocline becomes less of a boundary to cross for the (previously separated) deep water that the internal wave naturally brings to the surface.  Along with the shallow depths of the Chuchki Sea, this potentiates conditions for mixing. 
    The Chuchki Sea’s underwater topography consists of Mendeleyev Ridge to the northwest, the Chuchki Plain at the southern base of this ridge, the Chuchki Plateau to the northeast and the Arctic continental slope to the north (Arctic Ocean Encyclopædia Britannica Online, 2010).  According to research by Zhang et al. (2008), if the internal waves occurring in the Chuchki Sea had the same slope as the that of the Arctic continental slope, the strong shear and angle at which they encountered the slope would cause what are called boundary flows.  Boundary flows are intense currents caused by internal waves travelling up a continental slope (Zhang et al., 2008).  The internal wave rushes up the slope, carrying the unstable isocline until it reaches a critical point.  Here the current billows and then breaks on the slope, resulting in active mixing in what is usually a relatively stagnant ocean.  The diminishing ice coverage in the Arctic results in increased internal wave formation which in turn causes ocean mixing.  The Arctic Ocean water stratification levels are usually stable, so this increased mixing could affect delicate ecosystems, such as the conditions photoplankton blooms require in order to continue to survive.  

arctic phytoplankton bloom larger than the size of greece

Reduced ice levels and the increased mixing could also change the circulation in the Arctic; for example, impeding or potentiating the one major circulation channel: the Fram Strait.  This could in turn affect global water circulation, or thermohaline circulation.  Thermohaline circulation keeps the Earth’s overall temperature balanced.

the earth's oceanic "heating/cooling pump"

If this heating/cooling pump were to be altered or brought to a halt, the Earth’s delicate ecological, atmospheric, and geographic balances (among any other number of things) would be in disrupted, and the survival of life on the planet would be thrown into question.  Adding urgency to the need for more study is recent research suggesting cloud cover in the Arctic is decreasing, meaning increasing ice-melt and warming of surface waters (The American Geophysical Union & American Meteorological Society, 2008).
    Ice levels during the Arctic summer are diminishing, partly due to increased sun exposure and polar warming.  As a result, water is exposed and internal waves are more likely to form.  This potentiates conditions for ocean mixing, which in turn could affect ecosystems and thermohaline circulation as the receding ice worsens year by year.  The potentially profound and detrimental effects of the receding ice on the Earth’s environmental systems make the causes and effects of internal waves, specifically at the poles, an area of study requiring further research and attention.

References
Arctic Ocean. (2010). In Encyclopædia Britannica. Retrieved November 17, 2010, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/33188/Arctic-Ocean

Chukchi Sea. (2010). In Encyclopædia Britannica. Retrieved November 17, 2010, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/116851/Chukchi-Sea

Internal Waves in the Tsushima Strait (2006).  Retrieved from http://earthobservatory.nasa.gov/IOTD/view.php?id=7230

Internal Waves, Sulu Sea (2003).  Retrieved from http://earthobservatory.nasa.gov/IOTD/view.php?id=3586

Rainville et al. Observations of internal wave generation in the seasonally ice-free Arctic.     Geophysical Research Letters, 2009; 36 (23): L23604. doi:10.1029/2009GL041291

The American Geophysical Union and the American Meteorological Society (2008, April 1).  Inside The Clouds: Meteorologists Gather Important Information With 5-satellite 'A-Train' Group.  Science Daily.  Retrieved November 17, 2010, from http://www.sciencedaily.com/videos/2008/0402-inside_the_clouds.htm.

Tomczak, M. (2005) Introduction to Physical Oceanography [HTML]. Retrieved from http://www.es.flinders.edu.au/~mattom/IntroOc/lecture10.html.

Zhang et al.  Resonant Generation of Internal Waves on a Model Continental Slope. Physical Review Letters, 2008; PRL 100, 244504. doi:10.1103/PhysRevLett.100.244504