Harunur Rashid

Byrd Research Fellow, Byrd Polar Research Center, The Ohio State University (since 2007)
Ph.D. (Paleoceanography/Marine Geology) McGill University, 2002

My research interests involve resolving millennial-scale climate and ocean circulation variability from polar to tropical climate setting. I am also interested in understanding the dynamics of the Late Pleistocene Laurentide Ice-sheet and concomitant sediment and freshwater discharge-climate link which modulates the formation of the North Atlantic Deep water (NADW) and Labrador Sea Water (LSW). My current research projects can be grouped into the following:

1. Millennial-scale North Atlantic paleoclimate and paleoceanographic variability during the last 0.5 Myr. One of the most remarkable and precise evidence of abrupt climate change during the last glacial period have been documented in ice-cores as well as in marine and terrestrial records. These are known as the Dansgaard-Oeschger cycles which are bundled into Bond cycles of 5-10 ka and terminated by Heinrich Events, the massive iceberg rafting events from the North American ice-sheet, which released enormous amounts of meltwater. As a result, the freshwater is assumed to disrupt or even halt the formation of NADW preventing the penetration of the North Atlantic Current into higher northern latitudes. We documented these Heinrich and other high-frequency events in detail from the Labrador Sea and northwest Atlantic Ocean for the last glacial cycle. Sediments samples from the Integrated Ocean Drilling Program (IODP) Expedition 306 allowed us to extend our records of these ice-rafting events to the last four glacial cycles. Mg/Ca-SST and Cd/Ca techniques are used to reconstruct the surface and deep water perturbation as a result of the ice-rafting which are sourced from the neighboring continental ice-sheets.
2. Indian Ocean Monsoon (IOM) variability: The IOM is one of the major components of the modern tropical climate systems which is making profound changes in the lives of billions. Research over the last five years from in and around the tropics has shown a considerable degree of variability between the early and late Holocene which is attributed to the migration of the Intertropical convergence zone (ITCZ). With the potential warming looming in the horizon, it is predicted that the global climate might turn into like the early Holocene. But then the question is: what were the characteristics of IOM system during the early Holocene? What was the magnitude of runoff from the major rivers draining the Indian subcontinent as a result of the change in the intensity of monsoon? We have been working on the IOM project since 2005 and have reconstructed the first paleoclimatic history over the last 25 ka BP by making paired Mg/Ca and δ¹⁸O measurements on foraminiferal calcite in sediment cores retrieved from the Andaman Sea. We are working to extend this record to the Bay of Bengal and last three glacial cycles.
3. Paleoceanography of the Labrador Sea and northwest Atlantic Ocean. Studies over the last decade dedicated to assess the impact of freshwater and sediment release through the Hudson Strait and St. Lawrence Channel to modulate the Atlantic meridional overturning circulation (AMOC). Wallace Broecker of the LDEO of Columbia University suggested that the "outflow" from the St. Lawrence River was the main impetus causing the Younger Dryas cooling in the Northern Hemisphere by perturbing the NADW formation. However, later studies such as Anne de Vernal of UQAM questioned such a possibility. Keigwin and Boyle (1999) showed that the ice-rafted debris (IRD) were present in a core from the Bermuda Rise. Given the geographic location of the Bermuda Rise and the extent of the subtropical gyre in the northwest Atlantic, it was difficult to explain the occurrence of IRD at the Bermuda Rise.
   
   We have been using sediment cores collected off seaward of Hudson Strait and St. Lawrence Channel to explore whether YD and other freshwater signals can be documented. We also collected acquired deep-tow seismic profiles and sediment cores from the northern Sohm Abyssal Plain of the northwest North Atlantic. Our preliminary data suggest that the Hudson Strait was an important source for freshwater and sediment during the YD and other younger freshwater forcing events.
4. Artic Rivers Outflow history during warmer times. Studies over the last decade suggest that the summer Arctic sea-ice may disappear by 2020, a faster rate than most modelers anticipated. Such a forecast is important to the freshwater budget around the circum-Arctic as well as to the freshwater fluxes through the Bering and Fram Straits. To assess the Arctic Ocean freshwater delivery to the site of Meridional Overturning Circulation, the need to study past changes in such fluxes and summer sea-ice is required. In this regard, the last interglacial interval may be used as an analog for projected future conditions. Two novel proxies, Mg/Ca and Ba/Ca in planktonic foraminifera, are promising as revealed from the reconstruction of tropical rivers freshwater outflow which have not been employed in the Arctic Ocean. Estimating absolute temperatures based on Mg/Ca values alone may not be possible in the Arctic Ocean because the sensitivity of Mg/Ca at low temperature in Neogloboquadrina pachyderma (sinistral). Nevertheless, variations in Mg/Ca compared to δ¹⁸O will characterize relative temperature changes. The Ba/Ca in planktonic foraminifera has recently been shown as a proxy for freshwater input. We have started working on this project from 2008! We utilizing sediment cores collected during the HOTRAX 2005 expedition.

Selected publications

Publications: published papers

Rashid, H., and Boyle, E., (2008), Response to the comment on "Mixed-Layer deepening during Heinrich Events: a multi-planktonic foraminiferal δ¹⁸O approach". Science 320 (5880), 1161b, DOI: 10.1126/science.1153646. View Abstract

Rashid, H., and Boyle, E. (2007), Mixed-layer deepening during Heinrich Events: a multi-planktonic foraminiferal δ¹⁸O approach. Science 318, 439-441. View PDF | highlights of our paper in Nature

Rashid, H., Flower, B. P., Poore, R. Z. and Quinn, T. M. (2007), A ~25 ka monsoon variability record from the Andaman Sea. Quat. Sci. Rev. 26, 2586-2597. View PDF

Rashid, H. and Piper, D. J. W. (2007), Ice extent in Hudson Strait during Heinrich events H1 to H3. Can. J. Earth Sci. 44 (11), 1537-1549.

Rashid, H., and Grosjean, E., (2006), Detecting the source of Heinrich layers: an organic geochemical study, Vol. 21, PA3014, doi:10.1029/2005PA001240.

Hesse, R., Rashid, H., and Khodabakhsh, S., (2004), Fine-grained sediment lofting from meltwater-generated turbidity currents during Heinrich events, Geology 32, 449-452.

Rashid, H., Hesse, R., and Piper, D. J. W., (2003a), Distribution, thickness and origin of Heinrich Layer 3 in the Labrador Sea, Earth Planet. Sci. Let. 205, 281-293.

Rashid, H., Hesse, R., and Piper, D. J. W., (2003b), Origin of the unusually thick Heinrich layers HL-1 to HL-3 in the northwest Labrador Sea, Earth Planet. Sci. Lett. 208, 319-336.

Rashid, H., Hesse, R., and Piper, D.J.W., (2003c), Evidence for an additional Heinrich event in the Labrador Sea, Paleoceanography 18(4), 1077, doi: 10.1029/2003PA000913.

Thomas, F., Hardy, I., and Rashid, H., (2003), Bryozoan-rich layers in surficial Labrador Slope sediments: eastern Canadian Arctic, Can. J. Earth Sci. 40(3), 337-350.

Papers submitted

Rashid, H., Piper, D. J. W., and Flower, B. P., (2008), The meltwater signal of the Younger Dryas: a new assessment from the Labrador Sea and northwest Atlantic Ocean, to Earth Planet. Sci. Lett. (under review).

Rashid, H., Piper, D. J. W., Polyak, L., Flower, B. P., and Mansfield, C. (2008), Abrupt North Atlantic Deep Water slowdown coeval with Labrador Sea freshwater forcing at 10,200 years BP to Nature.

Papers to be submitted:

Rashid, H., Grützner, J., Lodestro, S., Voelker, A., Flower, B. P. & Quinn, T. M. (2008), Millennial-scale deep ocean ventilation and sea-surface variability during the last four glacial cycles: a new assessment for the Northern Hemisphere ice-sheet growth, for Nature.

Rashid, H., and Flower, B. P. (2008), Tropical Indian Ocean paleoclimatic history over the last 173,000 yr, to Geophys. Res. Lett.

Rashid, H. and Boyle, E. (2008), Testing two competing hypotheses of icebergs dispersion during H1, LGM, and H2 in the Labrador Sea: perspective from the Mg/Ca and δ¹⁸O on Neogloboquadrina pachyderma (s), to Paleoceanography.

Published Abstracts:

Rashid, H., Polyak, L., Adler, R. (2008), The last interglacial freshwater budget of the Arctic Ocean: planktonic foraminiferal Mg/Ca and Ba/Ca approach, SCAR/IASC meeting, St. Petersburg, Russia.

Rashid, H., Grützner, J., Lodestro, S., Voelker, A., Flower, B. P., Quinn, T. M. (2007), Millennial-scale deep ocean ventilation and sea-surface variability during the last four glacial cycles: a new assessment for the Northern Hemisphere ice-sheet growth, EOS Trans. AGU, 88(52), Fall Meet. Suppl., PP44B-07.

Boyle, E., Rashid, H., Goddard, E., Rodgers (2007), Deepening of the mixed layer during ice-rafting events: implication for the Meridional Overturning Circulation, EOS Trans. AGU, 88(52), Fall Meet. Suppl., PP44B-02.

Rashid, H., Lodestro, S., Rodgers, B., Flower, B. P., and Quinn, T. M., (2007), Evidence for the collapse of upper water masses during ice-rafting events: a multi-species planktonic foraminiferal δ¹⁸O approach, Geochim. Cosmoch. Acta 71 (15): A821-A821.

Rashid, H., Flower, B. P., Quinn, T. M., (2006), Tropical Indian Ocean paleoclimatic history over last 173,000 years, Fall AGU meeting, San Francisco.

Piper, D. J. W, Tripsanas, E, Rashid, H., (2006), The sedimentary record of the early Holocene Agassiz flood event on the deep continental margin of the Labrador Sea and Grand Banks, annual meeting of GAC-MAC, Montréal.

Rashid, H., Quinn, T. M., Poore, R. Z., (2005), Do the Bay of Bengal G. ruber δ¹⁸O data represents the diminishing trend of the Indian Ocean monsoon during the late Holocene? Chapman conference on "Tropical-Extratropical climatic teleconnections; A long-term perspective", Honolulu, HI, p.50.

Rashid, H., (2005), Does the nutrient distribution discrepancy between the Northern Indian Ocean basins during the LGM mean intrusion of Southern Ocean water? "Paleoceanography and paleoclimatology of the Southern Ocean" 21-23 Jan., University of Boulder, CO.

Rashid, H., Boyle, E., (2004), A ~100kyr SST record based on the Mg/Ca of Neogloboquadrina pachyderma (s) from the Labrador Sea, EOS Trans. AGU, 85(47), PP23B-1407.

Rashid, H., Grosjean, E., Higgins, S., (2004), A comparison of the impact of H2, H3, and H4 in the North Atlantic Ocean: A multi-proxy approach, ICP VIII, p.194.

Hesse, R., Rashid, H., Khodabakhsh, S., (2004), Heinrich Events as Times of the Main Sediment Supply to the Labrador Sea during the Late Pleistocene Glaciation, EOS Trans. AGU, 85(17), Jt. Assem. Suppl., C43A-21.

Rashid, H., Boyle, E., Keigwin, L., (2003a), A high-resolution 25 ka sea-surface temperature record from the NW Atlantic Ocean: foraminiferal Mg/Ca compared to δ¹⁸O and sediment parameters, EOS Trans. AGU, 84 (46), Fall Meet. Suppl., PP41A-01.

Rashid, H., Hesse, R., Piper, D. J. W., (2002), Differences between Labrador Sea and North Atlantic Heinrich Layers: implications for iceberg supply and meltwater discharge, EOS Trans. AGU, 83 (47), F937.

Rashid, H., Hesse, R., Vali, H., Piper, D. J. W., (2001), Linking of proximal to distal fluxes of the late Pleistocene LIS: Results from IMAGES cores MD95-2022, 23 and MD99-2233, Challenges of a Changing Earth, July 10-13, Amsterdam.

Rashid, H., Hesse, R., Piper, D. J. W., (2000), Was it melt-water outflow or ice-sheet discharge? A high-resolution study of ice-sheet dynamics from the high-latitude sector of the LIS during the LGM, EOS Trans. AGU, 81 (19), p.S21.

Rashid, H., Hesse, R., Piper, D. J. W., (1999), Records of Heinrich Events at the confluence of the distal Northwest Atlantic Mid-Ocean Channel and at the Imarssuak Mid-Ocean Channel of the North Atlantic, EUG 4(1), p.173.

Hesse, R., Khodabakhsh, S., Rashid, H., Piper, D. J. W., (1998), Late Pleistocene Glacial deposition on the Labrador margin sourced by ice-streams and Laurentide ice sheet collapse, EOS Trans. AGU, 79(45), F472.

Rashid, H., Austegard, A., (1997), 2D computer simulation of the South Viking Graben, North Sea, CSPG-SEPM joint international convention, Calgary, June 1-5, p.234.

Rashid, H., Austegard, A., (1997), 2D basin modeling of the abnormal Paleocene subsidence history of the Northern North Sea, Annual meeting of GAC-MAC, A.123.

Contribution to reports

2006: "The North Atlantic Paleoceanography: The last five million years" in Stein et al., EOS., 87(13), 28 March, 2006.

2005: Expedition Science Party, North Atlantic Climate 2: IODP Preli. Rept., 306.

2005: "Paleoceanography and paleoclimatology of the Southern Ocean", EOS Trans. Amer. Geophys. Union, 86(20), p.193.

2004: Ocean Research Interactive Observatory Networks (ORION) report, San Juan, PR.

2003: Ocean Observation Initiative-report, International Ocean Drilling Program, Seattle.

2002: Cruise report: CCGS Hudson cruise 2002-046 (open file), Geological Survey of Canada (Atlantic) (GSC) open file, Scotian Slope, August 15 - September 5th.

1998: Cruise report: CCGS Hudson cruise 1998-039 (open file), Geological Survey of Canada (Atlantic), Grand Banks-Sohm Abyssal Plain, August - September.

1997: Cruise report: CCGS Hudson 1997-048 (open file), Geological Survey of Canada (Atlantic), Churchill to Bedford Institute of Oceanography, 13th Sept. - 1st October.

Sea-going experience

JOIDES Resolution, IODP Expedition 306, Inorganic geochemist. Ponta Delgada, Azores- Dublin, Ireland, March-April, 2005.

CSS Hudson, HU2002046, Shipboard Scientist. Halifax, Nova Scotia- northwest Atlantic Ocean, August 2002.

CSS Hudson, HU1998039, Shipboard Scientist. Halifax, Nova Scotia-Sohm Abyssal Plain, August 1999.

CSS Hudson, HU1997048, Sedimentologist and seismic watchstander. Churchill, Manitoba- St. John’s, Newfoundland, June 1997.




	Phone: (614) 292-5040; Fax: (614) 292-4697
	E-mail:
	Snail Mail: Harunur Rashid, Ph.D. Byrd Polar Research Center The Ohio State University 1090 Carmack Rd Columbus, OH 43210 USA

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