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CITATION Genz, J., J. Aucan, M. Merrifield, B. Finney, K. Joel, and A. Kelen. 2009. Wave navigation in the : Comparing indigenous and Western scientific knowledge of the ocean. Oceanography 22(2):234–245, doi:10.5670/oceanog.2009.52.

COPYRIGHT This article has been published inOceanography , Volume 22, Number 2, a quarterly journal of The Oceanography Society. Copyright 2009 by The Oceanography Society. All rights reserved.

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downloaded from www.tos.org/oceanography Breaking Waves

Wa ve Navigation in The M arshall Islands Comparing Indigenous and Western Scientific Knowledge of the Ocean

By Joseph Genz, Jerome Aucan, Mark Merrifield, Ben Finney, Korent Joel, and Alson Kelen

Abstract Pacific seafarers developed indigenous navigational techniques to voyage between of instruments or charts. Ethnographic islands. In the Marshall Islands, navigators remotely sense land by detecting how investigations among surviving voyaging islands disrupt swells. A recent project to revitalize Marshallese voyaging aimed communities have sought to describe to understand the science of wave navigation. Local wave concepts are described various indigenous solutions to the navi- based on anthropological fieldwork with surviving navigators, including interviews gational tasks of orientation, steering a and experience sailing with them. The wave transformation processes that give rise course, estimating position, and making to these patterns are examined using navigators’ demonstrations at sea, wave buoy landfall (Gladwin, 1970; Lewis, 1972; measurements, satellite imagery, and wave model simulations. The scientific data Thomas, 1987; Feinberg, 1988). They account for one signal used by navigators to remotely detect land. Crossing wave describe how navigators use elabo- trains extend tens of kilometers in the lees of islands, which can be simulated as rate mental representations of space, refraction of the easterly trade wind swell. Navigators identified a superposition of embodied knowledge of the ocean, and incident swells with reflected waves 40 km upstream of islands. These reflected waves voyaging strategies to move through a were too weak to be detected by the wave buoy, but they are conceptualized similarly seemingly undifferentiated environment. within indigenous and scientific frameworks. Navigators described another pattern as One of the least understood naviga- a wayfaring link between distant atolls. This pattern does not clearly relate to a wave tion traditions comes from the Marshall transformation process, suggesting that Marshallese navigators also use concepts of Islands of Micronesia, where navigators the ocean that do not easily translate into oceanographic terms. developed a comprehensive system of wave piloting based on a common In troduction 3500–4000 years ago (Kirch, 2000). They land-finding technique for detecting Pacific seafarers began to explore and developed navigational techniques to islands by how they disrupt ocean swells settle the previously uninhabited islands sail their deep-sea voyaging canoes over and currents (Davenport, 1960; Ascher, of Remote Oceania (Eastern Melanesia, hundreds, and in some cases thousands, 1995; Finney, 1998). The Marshallese Micronesia, and ) about of kilometers of ocean without the aid archipelago comprises 34 coral atolls and

234 Oceanography Vol.22, No.2 300 km 165 170 15 0.5 m/sec b Figure 1. The Marshall Islands (a) are located in eastern Micronesia. The current climatology (b) shows how opposing Mejit 10 equatorial currents flow through the archipelago (Lagerloef et al., 1999). Arno a Hawaii 5 Marshall Guam Is.

area of B

EQUATOR

Solomon Islands

Fiji Figure 2. Captain Korent Joel, one of the last traditional navigators in the Marshall Islands, explains the wave concepts modeled within indigenous

1000 km teaching devices and demonstrates how he detects the wave patterns by Australia (at the equator) feeling how they alter the motion of an outrigger sailing canoe.

islands spread out in two parallel chains or intersections of opposing or nearly region of the Pacific. over 800 km along a southeast-northwest opposing swells (e.g., east and west Fortunately, a few Marshallese survive axis in the eastern part of Micronesia swells) (Winkler, 1898; Hambruch, today who learned traditional naviga- (Figure 1a). Strong, opposing equatorial 1912; Krämer and Nevermann, 1938; tion and voyaging in their youths. One currents (Lagerloef et al., 1999) make Davenport, 1960). However, a dramatic individual, a retired ship captain named navigation difficult (Figure 1b). In addi- decline in long-distance voyaging Korent Joel (Figure 2), recently called for tion, navigators may spend several days throughout the Marshalls in the latter a concerted effort to revive Marshallese out of sight of land because the tops of part of the twentieth century prevented navigation and voyaging before he and coconut palms on these low-lying atolls more detailed ethnographic investiga- others died without passing on their can only be seen 20 km offshore. The tions of the traditional wave concepts. knowledge to the younger genera- indigenous response to these naviga- In addition, previous studies have not tion. For assistance he turned to Waan tional challenges has been to remotely oceanographically validated the physical Aelo¯n¯ in Majel (Canoes of the Marshall sense land based on disruptions of inci- basis of the reported wave patterns or Islands), an organization that had previ- dent swells and currents. described the swell climatology in this ously documented the construction Exactly how Marshallese navigators find their way with reference to the Joseph Genz ([email protected]) is Lecturer, Department of , University waves has remained unclear. Researchers of Hawai‘i-Manoa, , HI, USA. Jerome Aucan is Research Scientist, Department in the late nineteenth century and early of Oceanography, University of Hawai‘i-Manoa, Honolulu, HI, USA. Mark Merrifield is twentieth century sailed with naviga- Professor, Department of Oceanography, University of Hawai‘i-Manoa, Honolulu, HI, USA. tors to understand their concepts of the Ben Finney is Professor Emeritus, Department of Anthropology, University of Hawai‘i- ocean, which center on either trans- Manoa, Honolulu, HI, USA. Korent Joel is Navigator, Waan Aelo¯n¯ in Majel (Canoes of the formations of the dominant easterly Marshall Islands), Republic of the Marshall Islands. Alson Kelen is Director, Waan Aelo¯n¯ in trade wind swell (Laubenfels, 1950) Majel (Canoes of the Marshall Islands), Republic of the Marshall Islands.

Oceanography June 2009 235 techniques of traditional outrigger anthropological fieldwork, oceano- Methods sailing canoes (Figure 3) and helped graphic modeling, and collaboration Anthropological Materials to revitalize the local sailing culture with local navigators and research coun- and Methods (Alessio and Kelen, 2004). To success- terparts has led to a detailed description Ethnographic data-collection methods fully transfer the navigational knowledge of the cultural revival of Marshallese were used to understand and describe to the next generation, leaders of Waan wave navigation (Genz, 2008). the indigenous concepts of the ocean. Aelo¯n¯ in Majel recognized the impor- In this paper, we describe the science Anthropological fieldwork took place tance of understanding the traditional of traditional Marshallese wave naviga- for 16 months between June 2005 wave concepts from a scientific perspec- tion. We examine indigenous knowl- and September 2006 on several atolls, tive and creating innovative pedagogical edge of the ocean through the lens of including Majuro, Rongelap, Namu, tools, such as computer simulations of anthropology and compare it to the Ujae, and Ailuk, where authors Genz and the waves. They requested the assis- oceanographic findings. Specific wave Kelen learned about traditional naviga- tance of University of Hawai‘i anthro- patterns used in Marshallese naviga- tion from Captain Korent Joel and other pologist Ben Finney, whose research in tion are described based on interviews navigation experts. The research was reconstructing and sailing Polynesian with surviving navigators and observa- conducted in the . voyaging canoes (Finney, 1977, 1979) tions made during their traditionally On land, Genz and Kelen learned by promoted the cultural renaissance of navigated voyages. The wave trans- explicit instruction through demonstra- Pacific voyaging (Finney, 1994, 2003, formation processes that give rise to tions, diagrams, and models. We also 2007). In response to Captain Korent’s these patterns are examined through conducted a variety of interviews and request, we developed a collaborative navigators’ demonstrations at sea, wave documented navigation stories, legends, and interdisciplinary project called buoy measurements, satellite imagery, chants, and songs. The ethnographic Kapeel in Meto (Indigenous Knowledge and wave model simulations. Through data were transcribed and translated for of the Ocean) that aimed to synergisti- such comparisons, we articulate the analysis. As the research progressed, we cally research navigation and revitalize similarities and differences between corroborated our understandings of the voyaging in the Marshall Islands (Genz indigenous and Western scientific indigenous concepts with the naviga- and Finney, 2006). A combination of knowledge of the ocean. tors. At sea, we observed navigation in practice and gained practical experience in order to learn some of the embodied knowledge of navigation. For example, in one experiment, Captain Korent guided a yacht 220 km between two atolls using traditional navigation techniques.

Oceanographic Materials and Methods The oceanographic data-collection methods aimed to understand the physical basis of the wave patterns used in traditional Marshallese naviga- tion. To characterize the wave field, we constructed a swell climatology for the Marshall Islands that described the seasonal changes in the dominant swell. Figure 3. A traditional Marshallese outrigger sailing canoe. The European Centre for Medium-Range

236 Oceanography Vol.22, No.2 Weather Forecasts (ECMWF) 40-Year and there are no neighboring atolls or of interest is not strongly affected by Re-analysis Data (ERA-40) used in the islands nearby to disrupt the regular the diffraction code. Similar results are study were obtained from the ECMWF flow of the dominant northeast trade obtained with and without the wave Data Server (ECMWF, 2008). wind swell. We used 180-m resolu- diffraction computation. We gained an overall visual under- tion bathymetry data for the Marshall standing from the collection of satellite Islands ( Reference Data and Indigenous Navigation imagery. We obtained an Advanced Models, 2008) to construct the SWAN Concepts and Models Spaceborne Thermal Emission and bathymetry grid and set the incoming Surviving Marshallese navigators set a Reflection Radiometer (ASTER) image swell from the east with a typical wave course, orient themselves, and track their of Mejit Island from the Marshall Islands period of 10 sec. The SWAN model grid progress according to the wave field, Environmental Protection Agency. was considerably larger than pictured in contrast to the other Micronesians We characterized swell conditions in Figure 8 so as to minimize model who rely primarily on the stars, and the using in situ wave data collected at boundary effects in the vicinity of the Polynesians who focus on both winds various locations by deploying a free- atoll. The spectral output from SWAN and stars (Lewis, 1972). The Marshallese floating directional wave buoy. As was decomposed into dominant swell navigators set an initial course based on it was not possible to reach Mejit by boat, we focused on the closely spaced atolls Majuro and Arno (see Figure 1b). Captain Korent treated these two atolls as marshallese navigators use wave patterns a single navigational target because they are intervisible. The Datawell Directional for course setting, orientation, estimating prog- Waverider G-4 wave buoy is designed ress, and remotely sensing land… to measure wave height, frequency, and direction through a GPS-based motion “ sensor. Directional wave spectra were obtained from 30-minute time series. trains by identifying multiple peaks in the known geographical configuration This method allowed us to identify the wave directional spectrum at each of the atolls and” orient themselves in different swells based on different wave grid point, and the swell trains were relation to the wave field. They concep- periods and directions. Captain Korent then used to construct the depicted wave tualize the wave field as swells arriving guided the wave buoy deployments. For orthogonals, lines that are perpendicular simultaneously from the four cardinal each salient wave pattern that Captain to the wave propagation direction and directions (east, west, north, and south). Korent detected, we deployed the wave parallel to local wave crests. The regu- They know from practical experience, buoy at three locations: near shore larity of the wave spectra allowed us to however, that not all four of these swells (1 km), off shore (20 km), and farther off connect the wave orthogonals unam- are present during normal wave condi- shore where he could not detect the wave biguously across the model domain. tions. The navigators detect swells by pattern (40 km). Our primary objective in using SWAN feeling the motion of the canoe. As the We used the Simulating Waves was to examine wave refraction as inci- voyage progresses, they remotely sense Nearshore (SWAN) model (Booij et al., dent swells from the east passed across the destination island by detecting 1999; Ris et al., 1999) to simulate wave the sloping topographies on the north particular wave patterns that indicate the transformations around island bathym- and south sides of the atoll, resulting direction and distance toward land. The etry. We focused on Mejit Island because in the distinctive crossing wave pattern navigators pilot, or guide, their canoes the ASTER imagery was available for it, in the lee. We note that SWAN does with reference to two different kinds of Mejit bathymetry is typical of many of have an algorithm for wave diffraction; wave patterns—waves surrounding atolls the smaller circular atolls in the region, however, the main crossing wave pattern and waves between atolls.

Oceanography June 2009 237 wind swell (Figure 4b). Superposition a b East Swell of the incoming trade wind swell and reflected wave energy produces distinc- kaaj in rojep tive wave patterns to the east of an atoll. aaj in rojep t t k t t The farthest extent of this reflected wave energy is called jur in okme directly Island Island east of an atoll and ka¯a¯j in ro¯jep to the nit in ko nit in ko nit in ko nit in ko jur in okme kaaj in rojep jur in okme northeast and southwest of an atoll. kaaj in rojep The navigators describe how the curved wave patterns jur in okme and ka¯a¯j in ro¯jep induce a vessel into a surfing Figure 4. Traditional Marshallese navigators diagram (a) how distinctively shaped waves extend seaward motion toward the direction of land. from any island in specific quadrants and can be detected up to 40 km away.Jur in okme refers to a We experienced this wave motion while curved wave that resembles the shape of a pole traditionally used to harvest breadfruit, ka¯a¯j in ro¯jep refers to a similar wave that resembles the curved shape of a traditional fishing lure, andnit in ko¯t refers Captain Korent searched for land during to a confused sea state by evoking the image of a cage used traditionally to capture birds. Traditional a series of wave buoy deployments to the navigators conceptualize (b) these waves as transformations of the easterly trade wind swell, which reflects seaward as it hits an island to formjur in okme, a region delineated by waves called ka¯a¯j in southeast of . Captain Korent r o¯ j e p , and then bifurcates to create nit in ko¯t, a zone of intersecting swells in the lee of the island. was guiding us to the northwest in the general direction of land by steering rela- tive to a dominant easterly swell when he detected the southeastern ka¯a¯j in ro¯jep K o¯ k¸ l al¸ (Navigation Signs) to a pole or branch used traditionally about 40 km offshore. The entire crew One way that Marshallese navigators to harvest fruit from a breadfruit tree. felt and saw how this particular wave remotely sense land is by detecting wave The end of this pole forks to create a lifted the stern of the vessel and pitched transformations of the dominant easterly V-shaped curve, which is used to twist the bow forward such that the vessel trade wind swell as it strikes and flows the breadfruit from the tree. According accelerated slightly in a surfing motion past atolls and small coral islands. The to the navigators, this curve resembles down the wave. Captain Korent adjusted navigators identified at sea several wave the shape of the easterly wave pattern his course based on how the ka¯a¯j in patterns that signal the presence of land. when reflected wave energy heaps up the ro¯jep directed the vessel. We felt the These navigation signs, called ko¯kl¸al¸, incoming swell. The term ka¯a¯j in ro¯jep wave pattern several more times until we extend seaward from any atoll or island refers to a traditional fishing lure made sighted the tops of coconut palm trees in specific quadrants and can be detected of shell or bone used to catch flying about 20 km away from land. up to 40 km away (Figure 4a). The rela- fish. The curve of this hook similarly The easterly trade wind swell wraps tive strength of these radiating wave resembles that of jur in okme and indi- around an atoll and crosses in the direct patterns indicates the distance toward cates the shape of the reflected waves to lee, creating a confused sea state called land, while the specific wave signatures the northeast and southeast of an island. nit in ko¯t. The navigators envision how indicate the direction of land. Literally meaning a “pit for bird fighting,” the easterly trade wind swell bifurcates The meanings of the local terms are nit in ko¯t evokes the image of a small around the atoll, such that the southern important in understanding how the cage used traditionally to capture birds. component flows northward and the Marshallese conceptualize the formation The horizontal and vertical intersecting northern component flows southward. of the wave patterns. The imagery evoked bars of the cage represent the crossing of They also conceptualize how the west by the terms relates to how the waves waves from multiple directions. swell reflects seaward. This lee wave affect the movement of a canoe, which The navigators conceptualize jur in crossing pattern alerts the navigator of the navigators use as a swell gauging okme, ka¯a¯j in ro¯jep, and nit in ko¯t as an atoll located upwind. The navigators instrument. The term jur in okme refers transformations of the easterly trade describe the multiple ways nit in ko¯t

238 Oceanography Vol.22, No.2 affects the motion of a canoe. We expe- Dilep (Wave Path Between Islands) from this line of waves or can no longer rienced and saw these movements to the The Marshallese navigators use ko¯kl¸al¸ detect it, they use the screen of ko¯kl¸al¸ west of Majuro atoll during a series of that result from transformations of the that surrounds each island to remotely wave buoy deployments. The dominant easterly trade wind swell to locate land, sense the destination island. easterly trade wind swell diminished in but they describe a different type of wave The navigators describe how to use energy as we moved into the protected pattern called dilep that forms between the dilep as a wayfaring signal, but we wave shadow west of the atoll. About pairs of atolls or islands. Dilep means cannot presently explain its forma- 10 km offshore, diminished swells from “backbone” and refers to waves that form tion. They conceptualize the dilep as the north-northeast and south-southeast a straight line between islands. The navi- the crossing of opposing or nearly rocked the vessel from side to side with gators describe how they set an initial opposing swells (Figure 5). For example, equal intensity. Captain Korent also indi- course toward the destination island and the crossing of east and west swells cated that he could feel a subtle pitching monitor the direction and strength of creates nodes of intersection called booj motion in response to the west swell and swells. As they sail out of sight of their (“knots”) that extend between northern its reflected wave, but the rest of the crew home island, they begin to search for and southern islands, and the crossing could not detect this movement. the dilep of the destination island. For of north and south swells creates similar The descriptions and use of the example, upon leaving Majuro atoll to booj that extend between eastern and various ko¯kl¸al¸ apply for normal sea the north (see Figure 1b), an observant western islands. From our scientific conditions, in which the dominant navigator could discern the wave signa- perspective, we cannot explain why this easterly trade wind swell is present. In tures of several northern atolls and then succession of distinctive waves forms on adverse sea conditions, the navigators feel his way toward land by staying on the direct sailing course between islands modify the directions of the ko¯kl¸al¸ one particular wave “path.” The naviga- rather than on either side of it. We also within their original conceptual frame- tors’ highest art is to maintain the canoe cannot explain why dilep toward multiple work. For example, during a traditionally on the dilep. In the event that they stray islands can be present simultaneously navigated voyage between two atolls, a storm replaced the easterly trade winds with a strong westerly wind. A wind- driven west swell dominated the ocean Island and masked other swells and most of the more subtle ko¯kl¸al¸. The destination booj island lay 200 km directly west of the home island. Under normal conditions, Captain Korent should have been able West East to detect the leeward nit in ko¯t of the Swell Swell home island as we departed and then searched for the windward jur in okme of dilep the destination island as we approached it. Instead, he mentally reversed the directions of the ko¯kl¸al¸ in relation to the islands, envisioning how the west- wind-driven swell would create a zone of Island confused and diminished seas in the lee Figure 5. Traditional Marshallese navigators describe a wave pattern of the destination island. Indeed, about called dilep that forms between pairs of islands. They conceptu- alize dilep as the crossing of opposing or nearly opposing swells 30 km away from land, he detected this (e.g., east and west swells), which creates nodes of intersection (booj) nit in ko¯t eastward of the island. between islands.

Oceanography June 2009 239 when the wave field is not characterized of swells and their intersections, and the Third, the wapepe models the dilep, or by multiple, opposing swells. resulting sea conditions (Winkler, 1898). sailing courses between pairs of atolls. In In practice, the dilep is perhaps the The wapepe models the interplay of this perspective, the entire latticework most difficult of the wave patterns to oceanographic phenomena and land represents the ocean. The center point of detect. At sea during several voyages masses by uniformly depicting four each short edge of the latticework (right, and wave buoy deployments, Captain swells from perpendicular directions, left, up, and down) represents an island Korent identified the dilep, but we could symmetrically placing islands and in the eastern, western, northern, and not discern the motion of this wave reducing them to points, and reducing southern parts of the ocean. The central pattern from the wave field. During the wave patterns to lines or points straight vertical line indicates the dilep the traditionally navigated voyage of intersection (Ascher, 1995). The between northern and southern islands, described previously, Captain Korent wapepe can be interpreted in three ways and the central straight horizontal could not detect the dilep, as the strong (Figure 6b). First, it models the wave line refers to the dilep between eastern storm-driven westerly swells masked field. The intersecting lines at the center and western islands. the presence of other swells. Without of the latticework represent an island, these guiding waves, he could not easily and the four overlapping curves indicate Wave Observations and monitor his progress, but he remotely the directions from which swells flow Model Simulations detected land by feeling the nit in ko¯t of (east, west, north, and south). Second, Remote and in situ wave measurements the destination island. Captain Korent’s the wapepe models the wave transforma- and wave models validate several indig- successful landfall without the aid of the tions (ko¯kl¸al¸) of the easterly trade wind enous wave concepts and provide new dilep illustrates how navigators’ practical swell. With the center of the latticework data on the regional wave climate and experience at sea differs from their ideal- representing an island, the intersections island-induced wave transformations. ized concepts of wave transformations. of the four curves indicate the posi- A regional swell climatology for the tions of the windward jur in okme and archipelago, constructed from a global Wapepe (Indigenous Wave Model) ka¯a¯j in ro¯jep and the leeward nit in ko¯t. wave model data set (ECMWF, 2008; The navigators modeled the wave field and swell transformations for us by weaving the mid-ribs of coconut palms (Cocos nucifera) or thin sections of the H aerial roots of pandanus (Pandanus a b b f c tectorius) into a latticework of lines and curves. They constructed three varieties e of models. One of these, the wapepe l (Figure 6a), is strikingly similar to those o m K A g I documented in the late nineteenth n and early twentieth centuries (Schück, d 1902). Scholars initially interpreted these models as “stick charts,” believing they showed the positions of islands, sailing courses, and sea conditions (Gulick, J Figure 6. Traditional Marshallese navigators constructed a wave model called wapepe (a) by lashing 1862; Meinicke, 1863). Later studies, pandanus roots into a latticework. A diagram of the wapepe (b) shows how swells approach an island however, showed that they were not (point A) from the east, west, north, and south (curves b, c, d, and e, respectively). Wave transformations nautical charts or instruments, but rather of the easterly swell form jur in okme (point m), ka¯a¯j in ro¯jep (points l and n), and nit in ko¯t (point o). The crossing of swells from the east and west form adilep (line f) between a northern island (point H) teaching devices that depicted the direc- and a southern island (point J), and the crossing of swells from the north and south form a dilep (line g) tion of predominant swells, the bending between an eastern island (point I) and a western island (point K).

240 Oceanography Vol.22, No.2 Nov- Mar 300 km 165 170 49° 15 Figure 7. A regional swell climatology model, constructed from a global wave model data set (European Centre for Medium-Range Weather Forecasts [ECMWF], 2008), shows that the swell direction varies Apr- seasonally with the trade winds, arriving from the northeast in boreal June, winter and the southeast in boreal summer. A southwest swell Oct sporadically complements the east trade wind swell, but does not contribute substantially to the overall wave field. 83° Mejit 10

July- Sept transformations around islands larger Arno Majuro than Mejit. We suspect that disturbances 113° of the trade wind wave field may stretch for tens of kilometers in the lee of the 5 larger islands. These longer wakes may

224°Aug- be due to the blocking of the domi- Dec nant swell by the island, which allows directionally spread wave components to create a crossing wave pattern in the island shadow zone (Chawla Figure 7), shows that the dominant swell an east swell with a 10-sec period and Tolman, 2008). direction varies seasonally with the trade transforms at, and past, the Mejit Island To further validate the lee-wave winds, arriving from the northeast in bathymetry (Figure 8b). The bending of pattern and to search for reflected boreal winter and the southeast in boreal crests is due primarily to wave refrac- wave energy, we gathered directional summer. Southwest swells occur from tion over the sloping sides of the island. wave data at navigation signs (ko¯kl¸al¸) August through December, but these Model tests with and without wave surrounding the closely spaced Majuro intermittent events are limited in dura- diffraction show little difference in the and Arno atolls through a series of wave tion and would seem to be unreliable simulated lee wave field, except in a buoy deployments under the guidance for navigational purposes. Extratropical small zone in the immediate shadow of of navigator Captain Korent (Figure 9). storms in the North Pacific can lead to the island. The model indicates that the The data are consistent with a bending unexpected waves, such as an event in crossing lee wave pattern extends tens of of 10-sec period easterly swells into December 2008 that caused flooding kilometers downstream, consistent with north and south components as they in the Marshall Islands. However, these the ASTER image and with descriptions encounter the atolls; however, multiple storms are too strong and irregular provided by the navigators. Although the incident swell trains from multiple direc- for navigation. lee-wave crossing pattern is well docu- tions during the experiment made it To visualize how the dominant east- mented in the oceanographic literature difficult to validate the lee-wave crossing erly trade wind swell transforms as it (Bascom, 1964; Massel, 1996), we have pattern conclusively. As described previ- encounters the atolls, we first analyzed not found descriptions of the pattern so ously, a specific motion of the vessel satellite imagery. An ASTER image far from the island source. The present was detected west of Majuro that the shows how an east swell bifurcates version of SWAN does not simulate wave navigator identified as nit in ko¯t. At this northward and southward around Mejit reflection from the atoll shoreline and location, diminished swells arriving from Island, resulting in a zone of intersecting the ASTER image does not seem to indi- the north-northeast and south-southeast wave trains in the island lee (Figure 8a). cate the presence of reflected wave crests rocked the vessel from side to side Navigators identified the regions of inter- to the east of Mejit. with equal force. secting swells in the image as nit in ko¯t. We do not have ASTER images or The wave buoy data do not indicate The SWAN wave model shows how in situ observations to document wave reflected energy in the regions east of

Oceanography June 2009 241 a Arno designated by the navigator as jur a in okme and ka¯a¯j in ro¯jep. Apparently, much of the incoming swell is dissipated on the atoll reefs, resulting in weak wave reflection. However, we felt how a vessel intermittently pitched forward in response to swells with increased wave heights 40 km offshore of the south- eastern side of Arno. As described previ- ously, Captain Korent guided us toward land by following this ka¯a¯j in ro¯jep. It is likely that an expert may be able to

0 1 1 2 km detect an extremely weak or intermittent

0 1 1 2 km reflected wave signal that is below the sensitivity threshold of the buoy. 7 2 To understand the physical basis 7 b 2 1.8 of the dilep, we gathered directional 6 b 1.8 wave data along the dilep extending 6 1.6 from Majuro to Aur, an atoll 100 km 1.6 5 1.4 directly north of Majuro. Several times 5 1.4 ) 1.2 during this northern voyage, Captain 4 ) 1.2 Korent described a rocking motion from 4 1 intersections of east and west swells. He 3 1

Distance (km 0.8 followed a succession of these booj along 3

Distance (km 0.8 the dilep toward land, but the wave buoy 0.6 2 data from these locations indicated only 2 0.6 0.4 an east swell. However, our field study 1 0.4 0.2 was limited to a short series of wave 1 0.2 buoy deployments for such an extensive 0 0 012345678 9 Wave wave pattern. 0 0 0123Distance45 (km) 678 Height (m) 9 Wave Distance (km) Height (m) Discussion Figure 8. Wave transformations at Mejit Island. An Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image (a) shows how an east swell The application of the global wave clima- bifurcates northward and southward around the island, resulting in a zone of tology model to the Marshall Islands intersecting wave trains in the lee. Courtesy of the Marshall Islands Environmental shows that this region of Oceania is Protection Agency. A Simulating Waves Nearshore (SWAN) model simulation (b) of a unimodal, 10-sec period easterly swell shows similar results in terms of characterized by a dominant easterly significant wave height (color). Crests are shown in black and 50-m contours in trade wind swell for the entire year. The gray. The overall energy is reduced in the direct lee of the island, and the bending of crests is due primarily to wave refraction over the sloping sides of the atoll. This model supports navigators’ emphasis on crossing lee wave pattern extends tens of kilometers downstream of the island. detecting transformations of the trade wind swell, but contrasts with the local conceptualization that swells flow consis- tently from the four cardinal directions. This apparent incompatibility between local and scientific knowledge systems

242 Oceanography Vol.22, No.2 may reflect differences in terminology language rather than a refracted east okme and ka¯a¯j in ro¯jep are conceptual- and temporal perspectives. First, the swell. This combination of local termi- ized similarly within indigenous and Marshallese navigators name each of nology and a temporal perspective in the scientific frameworks as reflections of the four main swells, but a four-point immediate present helps explain why the the trade wind swell. The steep island orientation framework can only be used local conceptualization of the wave field slopes are favorable for wave reflec- to indicate direction very generally. differs from the wave climatology model. tions; however, reflected wave energy For example, a swell coming from the The oceanographic data support the was not detected, perhaps due to the northeast could equally be called an east physical basis of the navigation sign nit limited duration of the buoy tests and swell or a north swell. Second, the termi- in ko¯t as a lee-wave crossing pattern, and the inability to sample a wide range nology may focus on the immediate this oceanographic perspective conforms of wave conditions. sea conditions rather than tracing the strongly with the indigenous explana- The lack of data to support the naviga- wave transformations through time. For tion. However, additional measurements tors’ conceptualization and use of dilep example, an east swell that is refracted by are needed to understand the physical suggests that it does not translate easily an island to flow to the north is referred basis of the other wave patterns (jur in into oceanographic terms. This indig- to as a north swell in the Marshallese okme, ka¯a¯j in ro¯jep, and dilep). Jur in enous concept requires the presence of a persistent sea state with four swells flowing from the cardinal directions. However, the swell climatology shows

171°00' 171°30' 172°00' that opposing easterly and sporadic southwesterly swell characterize the wave field only during a few months of the year. It is possible that navigators 7°30' can detect other swells that are too weak to be measured and modeled. Even if swells arrive from opposite directions, however, their refracted crests would intersect only a few hundred meters DE offshore. Within sight of land, these wave Majuro transformations would not be naviga- Arno

tionally useful. Waves may transform as C 7°00' D they pass through the spatially varying current field (see Figure 1b); however, we BB were not able to link this process to dilep AA between all possible island pairs. Alternately, dilep might be a concep- tual device rather than an oceanographic -6000 -5000 -4000 -3000 -2000 -1000 0 phenomenon. Navigators throughout Depth (m) Remote Oceania steer their voyaging Figure 9. Wave displacement data near Majuro and Arno atolls. Arrows at five locations show indi- canoes during the day by calibrating vidual swell components scaled to wave height. The wave field to the east of Arno is characterized the angle of dominant swells to the by a primary southeast swell and a smaller east-northeast swell (A–C). The data do not indicate reflected energy, which the navigator identified aska¯a¯j in ro¯jep (B). These swells bifurcate into north fading stars at dawn (Lewis, 1972). and south components as they encounter the bathymetry (color), such that the wave field to the Observations during traditionally navi- west of Majuro is characterized by diminished south-southeast and north-northeast swells (E). The navigator identified this crossing lee wave pattern asnit in ko¯t. Black arrows indicate a south swell gated voyages suggest that Marshallese that does not contribute to the formation of nit in ko¯t. navigators set their initial course toward

Oceanography June 2009 243 the approximate geographic direction in okme and ka¯a¯j in ro¯jep). Second, the do not necessarily reflect the views of the destination island and then cali- modeled wave field shows one dominant of NOAA or any of its subagencies. brate it to the angle of the swells. If they swell while navigators’ conceptualize UNIHI-SEAGRANT-OP-06-37. This can detect subtle swells from several four swells. Third, the scientific data do project is also funded by the National directions, they may be able to steer by not account for the indigenous concept Science Foundation under Grant No. 514594, the Wenner-Gren Foundation for Anthropological Research, Inc. under Grant No. 7282, and Mobil Oil further investigations may reveal whether… Micronesia. The authors would like to recognize several Marshallese orga- differences between local and Western scientific nizations for their support, including knowledge reflect differences in terminology Waan Aelo¯n¯ in Majel (Canoes of the or discrepancies between instrument sensitivity Marshall Islands), the Rongelap Atoll “ Local Government, the and perceptions. Local Government, the Marshall Islands Fisheries and Nautical Training Center, the Marshall Islands Environmental Protection Agency, the Marshall Islands following the same angle of intersec- of wave patterns between islands (dilep). Marine Resource Authority, and the tion. However, the navigators maintain ”Further investigations may reveal Alele Museum. We wish to thank that following the dilep is distinct whether such differences between local Iroijlaplap (high chief) Imata Kabua and from steering by the relative angle and Western scientific knowledge reflect Iroij (chief) Mike Kabua for granting of the swells. differences in terminology or discrepan- permission to conduct the naviga- cies between instrument sensitivity and tion project, and Isao Eknilang, Alton Conclusion human perceptions. It is also possible, Albious, Anno Aisaia, Willie Mwekto, Marshallese navigators use wave patterns however, that the Marshallese have Francis Livai, Thomas Bokin, Lijohn for course setting, orientation, esti- alternative ways of conceptualizing the Eknilang and Mejon River for sharing mating progress, and remotely sensing ocean that do not easily fit within a their navigational knowledge. In addi- land, which supports the notion that scientific framework. tion, we wish to thank Richard and Chris Marshallese navigation is a system of Barrie, Eric Nystrom, and Priam Kanealii wave piloting (Davenport, 1960; Ascher, Acknowledgements for providing their sailing vessels; 1995; Finney, 1998). Our oceanographic This paper is based on the results of Oliver Vetter for assisting with the wave perspective conforms strongly with one a collaborative and interdisciplinary buoy deployments; Dennis Alessio, indigenous concept—a lee-wave crossing revival project. It is funded in part by Jill Luciano, Rachel Miller, and Lance pattern that results from refraction of the a grant/cooperative agreement from Samura for providing extensive admin- easterly trade wind swell (nit in ko¯t). Such the National Oceanic and Atmospheric istrative support; and Nancy Hurlbirt converging explanations highlight simi- Administration, Project #R/EP-27, for assisting with Figure graphics. We larities between indigenous and Western which is sponsored by the University presented this paper as a poster at the scientific knowledge (Agrawal, 1995). of Hawai‘i Sea Grant College Program, November 2007 International Workshop The other indigenous concepts of the SOEST, under Institutional Grant on Wave Hindcasting and Forecasting ocean are presently more difficult to No. NA05OAR4171048 from NOAA and Coastal Hazard Symposium on the translate into oceanographic terms. First, Office of Sea Grant, Department of North Shore, Hawai‘i and we are grateful the scientific data do not account for the Commerce. The views expressed for the encouragement we received. We reflected windward wave patterns (jur herein are those of the authors and also wish to gratefully acknowledge Nina

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