Sea Level Change in the Western James Bay Region of Subarctic Ontario: Emergent Land and Implications for Treaty No. 9

In 1905 and 1906, the Cree of the southwestern James Bay region signed Treaty No. 9 whereby they relinquished to the Canadian government their claim to the lands south of the Albany River (the northern boundary of the province of Ontario at the time). The official text of Treaty No. 9 made no mention of land submerged below water cover, and thus the Cree did not relinquish such regions at that time. By contrast, the Cree of the northwestern James Bay and southwestern Hudson Bay region who signed the 1929–30 Adhesions to Treaty No. 9 relinquished their claims to “land covered by water” for the area bounded on the south by the northerly limit of Treaty No. 9, as this clause was specifically included in the text of the adhesion. The issue of “land covered by water” is significant because the western James Bay region has been, and will continue to be, subject to sea level changes associated with ongoing adjustments due to the last ice age and modern global warming signals. In the absence of detailed maps, we used models of these processes, constrained by available geophysical and geodetic data sets, to retrodict shoreline changes and the rate of land emergence over the last two centuries within the boundaries specified by Treaty No. 9. We also project shoreline migration to the end of the 21st century within the same region. The rate of land emergence since 1905 in the area south of the Albany River is estimated as ~3.0 km2/yr. Over the next century, land will continue to emerge in this region at a mean rate of ~1.4 km2/yr. This emergent land should be a subject of consideration within any comprehensive land claim put forward by the Cree; in this regard, it will be interesting to see how the Canadian judicial system and the Comprehensive Claims Branch handle the novel issue of emergent land.En 1905 et 1906, les Cris du sud-ouest de la région de la baie James ont signé le Traité no 9, par le biais duquel ils ont cédé au gouvernement du Canada leur droit de revendication des terres au sud de la rivière Albany (la limite nord de la province de l’Ontario à l’époque). Le texte officiel du Traité no 9 ne faisait aucune mention des terres submergées sous l’eau, si bien que les Cris n’ont pas renoncé à ces régions à ce moment-là. En revanche, les Cris du nord-ouest de la baie James et du sud-ouest de la baie d’Hudson qui ont signé les adhésions au Traité no 9 (1929-1930) ont renoncé à leurs revendications aux « terres recouvertes d’eau » dans la zone délimitée au sud par la limite nord du Traité no 9, puisque cette clause était expressément incluse dans le texte de l’adhésion. La question des « terres recouvertes d’eau » est importante parce que l’ouest de la région de la baie James a été et continuera d’être assujettie aux variations du niveau de la mer liées aux ajustements continus découlant de la dernière période glaciaire et des récents signes de réchauffement planétaire. En l’absence de cartes détaillées, nous avons utilisé des modèles de ces processus, limités par les ensembles de données géophysiques et géodésiques disponibles, pour déterminer de façon rétrospective les changements du littoral et le taux d’émergence des terres au cours des deux derniers siècles dans les limites précisées dans le Traité no 9. Nous faisons également une projection de la migration du littoral jusqu’à la fin du XXIe siècle dans cette même région. Le taux d’émergence des terres depuis 1905 dans la région au sud de la rivière Albany est estimé à ~3,0 km2/année. Au cours du prochain siècle, les terres continueront d’émerger dans cette région au taux moyen de ~1,4 km2/année. Ces terres émergées devraient être prises en compte dans toute revendication territoriale globale présentée par les Cris. À cet égard, il sera intéressant de voir comment le système judiciaire canadien et la Direction générale des revendications globales traiteront cette nouvelle question des terres émergées

Revisiting tectonic corrections applied to Pleistocene sea-level highstands

Tectonic displacement contaminates estimates of peak eustatic sea level (and, equivalently, minimum continental ice volumes) determined from the elevation of Quaternary interglacial highstand markers. For sites at which a stratigraphic or geomorphic marker of peak Marine Isotope Stage (MIS) 5e sea level exists, the standard approach for estimating local tectonic uplift (or subsidence) rates takes the difference between the elevation of the local highstand marker and a reference MIS 5e eustatic value, commonly chosen as +6 m, and divides by the age of the marker. The resulting rate is then applied to correct the elevation of all other local observed sea-level markers for tectonic displacement, including peak highstands of different ages (e.g., MIS 5a, MIS 5c and MIS 11), under the assumption that the tectonic rate remained constant over those periods. This approach introduces two potentially significant errors. First, the peak eustatic value adopted for MIS 5e in most previous studies (i.e., +6 m) is likely incorrect. Second, local peak sea level during MIS 5e is characterized by significant departures from eustasy due to glacial isostatic adjustment in response to both successive glacial–interglacial cycles and excess polar ice-sheet melt relative to present day values. We use numerical models of glacial isostatic adjustment that incorporate both of these effects to quantify the plausible range of the combined error and show that, even at sites far from melting ice sheets, local peak sea level during MIS 5e may depart from eustasy by 2–4 m, or more. We also demonstrate that the associated error in the estimated tectonic rates can significantly alter previous estimates of peak eustatic sea level during Quaternary highstands, notably those associated with earlier interglacials (e.g., MIS 11)

The Interaction of Ice Sheets with the Ocean and Atmosphere

A rapidly melting ice sheet produces a distinctive geometry of sea level (SL) change. Thus, a network of SL observations may, in principle, be used to infer sources of meltwater flux. We outline a new method, based on a Kalman smoother, for using tide gauge observations to estimate the individual sources of global SL change. The Kalman smoother technique iteratively calculates the maximum likelihood estimate of Greenland and West Antarctic ice sheet melt rates at each time step, and it allows for data gaps while also permitting the estimation of non-linear trends. We have also implemented a fixed multi-model Kalman filter that allows us to rigorously account for additional contributions to SL changes, such as glacial isostatic adjustment and thermal expansion. We report on a series of detection experiments based on synthetic SL data that explore the feasibility of extracting source information from SL records before applying the new methodology to historical tide gauge records. In the historical tide gauge study we infer a global mean SL rise of ~1.5 ± 0.5 mm/yr up to 1970, followed by an acceleration to a rate of ~2.0 ± 0.5 mm/yr in 2008. In addition to its connection to SL, Greenland and its large ice sheet act as a barrier to storm systems traversing the North Atlantic. As a result of the interaction with Greenland, low-pressure systems located in the Irminger Sea, between Iceland and Greenland, often produce strong low-level winds. Through a combination of modeling and the analysis of rare in-situ observations, we explore the evolution of a lee cyclone that resulted in three high-speed-wind events in November 2004. Understanding Greenland’s role in these events is critical in our understanding of local weather in this region.Ph

Quantifying the Sensitivity of Sea Level Change in Coastal Localities to the Geometry of Polar Ice Mass Flux

It has been known for over a century that the melting of individual ice sheets and glaciers drives distinct geographic patterns, or fingerprints, of sea level change, and recent studies have highlighted the implications of this variability for hazard assessment and inferences of meltwater sources. These studies have computed fingerprints using simplified melt geometries; however, a more generalized treatment would be advantageous when assessing or projecting sea level hazards in the face of quickly evolving patterns of ice mass flux. In this paper the usual fingerprint approach is inverted to compute site-specific sensitivity kernels for a global database of coastal localities. These kernels provide a mapping between geographically variable mass flux across each ice sheet and glacier and the associated static sea level change at a given site. Kernels are highlighted for a subset of sites associated with melting from Greenland, Antarctica, and the Alaska-Yukon-British Columbia glacier system. The latter, for example, reveals an underappreciated sensitivity of ongoing and future sea level change along the U.S. West Coast to the geometry of ice mass flux in the region. Finally, the practical utility of these kernels is illustrated by computing sea level predictions at a suite of sites associated with annual variability in Greenland ice mass since 2003 constrained by satellite gravity measurements.Harvard University; NASA [NNX17AE17G, NNX17AE18G, 80NSSC17K0698]; NSF [ICER-1663807]6 month embargo, April 2018This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

The sea-level fingerprints of ice-sheet collapse during interglacial periods

Studies of sea level during previous interglacials provide insight into the stability of polar ice sheets in the face of global climate change. Commonly, these studies correct ancient sea-level highstands for the contaminating effect of isostatic adjustment associated with past ice age cycles, and interpret the residuals as being equivalent to the peak eustatic sea level associated with excess melting, relative to present day, of ancient polar ice sheets. However, the collapse of polar ice sheets produces a distinct geometry, or fingerprint, of sea-level change, which must be accounted for to accurately infer peak eustatic sea level from site-specific residual highstands. To explore this issue, we compute fingerprints associated with the collapse of the Greenland Ice Sheet, West Antarctic Ice Sheet, and marine sectors of the East Antarctic Ice Sheet in order to isolate regions that would have been subject to greater-than-eustatic sea-level change for all three cases. These fingerprints are more robust than those associated with modern melting events, when applied to infer eustatic sea level, because: (1) a significant collapse of polar ice sheets reduces the sensitivity of the computed fingerprints to uncertainties in the geometry of the melt regions; and (2) the sea-level signal associated with the collapse will dominate the signal from steric effects. We evaluate these fingerprints at a suite of sites where sea-level records from interglacial marine isotopes stages (MIS) 5e and 11 have been obtained. Using these results, we demonstrate that previously discrepant estimates of peak eustatic sea level during MIS5e based on sea-level markers in Australia and the Seychelles are brought into closer accord